Benrus 3 Star Self-Winding. Can’t Open the Case - Again!

[Latetothegame]

I recently posted about my inability to determine exactly how to open a vintage Sovereign watch.  As some of you may recall, with a lot of help from people in this group, I eventually figured out that the watch was a front loader and got everything worked out.  The watch is now running great and in my collection.  For my very next project I purchased a 1950s Benrus 3 Star 25 Jewel Self-Winding watch.  I wanted to expand my experience into automatics.  I figured since Sovereign was made by Benrus and both leaned heavily into front loading single piece case backs, I shouldn’t have a problem.  I was wrong.  Let me try to get to the point.  I have added pictures to help provide as much info as possible.  This watch appears to clearly have a seam in the case back.  There seems to be an opening on the rear of the front half of the case to allow the stem to slide out of the back of the case (possibly without being removed). The case DOES NOT say “Open Through Crystal” as many Benrus watches do.    The crystal is a “low dome” style and my crystal lift (not the highest quality )cannot seem to get a grip on the side of it as it is almost 100% angled with no real straight piece to grasp.  I read in an old discussion on this site (where someone was having a similar issue) that some Benrus watches open by pushing the crystal and movement through the case in a way that actually pushed the case back off.  I can find NO obvious place intended for prying the case back off but there definitely appears to be a seam.  See pics.  
Once again, I would greatly appreciate your input and advice.  Thanks.

 

 

 

 

 

 

 

Edited June 30, 2024 by Latetothegame

[rjenkinsgb]

To me, that looks like a removable back.

The slot around the stem in the front case half appears to be for the movement to release through the back,  plus the rear text is not in perfect alignment with the case, which implies the back has been removed in the past.

I'd expect it to split at the "step" level, behind the stem & front case body, not at the bezel or crystal.

[caseback]

Benrus indeed has models with a kind of 2-piece case where you have to press on the crystal to remove the back after you remove the crown (split stem). Roamer had a simular system. Benrus sold specific tools for that purpose. I had one of those tools, but it was incomplete (just the box and the press) so I sold that to a Benrus collector.

You can still find these sets. Often the pictures also show the instructions for removing and assembly. There's on on the bay right now:

 

[Neverenoughwatches]

7 hours ago, Latetothegame said:

I recently posted about my inability to determine exactly how to open a vintage Sovereign watch.  As some of you may recall, with a lot of help from people in this group, I eventually figured out that the watch was a front loader and got everything worked out.  The watch is now running great and in my collection.  For my very next project I purchased a 1950s Benrus 3 Star 25 Jewel Self-Winding watch.  I wanted to expand my experience into automatics.  I figured since Sovereign was made by Benrus and both leaned heavily into front loading single piece case backs, I shouldn’t have a problem.  I was wrong.  Let me try to get to the point.  I have added pictures to help provide as much info as possible.  This watch appears to clearly have a seam in the case back.  There seems to be an opening on the rear of the front half of the case to allow the stem to slide out of the back of the case (possibly without being removed). The case DOES NOT say “Open Through Crystal” as many Benrus watches do.    The crystal is a “low dome” style and my crystal lift (not the highest quality )cannot seem to get a grip on the side of it as it is almost 100% angled with no real straight piece to grasp.  I read in an old discussion on this site (where someone was having a similar issue) that some Benrus watches open by pushing the crystal and movement through the case in a way that actually pushed the case back off.  I can find NO obvious place intended for prying the case back off but there definitely appears to be a seam.  See pics.  
Once again, I would greatly appreciate your input and advice.  Thanks.

 

 

 

 

 

 

 

Patent numbers can sometimes give us clues to things like this .

[RichardHarris123]

If it is a split stem, you could try the compressed air method. 

[caseback]

8 minutes ago, RichardHarris123 said:

If it is a split stem, you could try the compressed air method. 

Well in this case  compressed air will probably blow the crystal off, and you need that to push the back / centre piece of the case out. 

26 minutes ago, Neverenoughwatches said:

Patent numbers can sometimes give us clues to things like this .

Good digging!

Indeed the same principle as Roamer's. Different patent?

 

 

[Latetothegame]

Thank you all for your input and information.  So, I know this isn’t the tool specifically intended for the job, but do you think I could get away with using this case press tool as shown in the attached pics?  I already have it and I don’t know if I want to invest in the Benrus tool since I don’t really anticipate working on a lot of these watches.  I’m thinking there’s a risk the lugs may not be able to withstand the pressure but they seem pretty solid.  Am I missing something else?  Thanks. 

And I obviously would need to remove the stem first.  

[caseback]

Worth a try. Should work. I'm not a big fan of these presses though, as it is difficult to "manage" the amount of force. That's why I practically never use the Bergeon 5500  but prefer the screw down type press:

The Roamer sets come up for sale often, and are usually cheap. And as a watchmaker's purpose in life is to collect tools....

 

[watchweasol]

As with all watches to get the movement out employed different methods,  screw back,   Press on backs etc but we cannot assume they are all the same. I have had watches that to get the movement out entails first removing the back. Then the glass and bezel , then removing the case screws and lifting the movement through the front. When investigating  how it opens up be very careful and explore all avenues don’t just dive in with a case knife, I have come across some gouged up cases in the past.

[Latetothegame]

Thanks again guys!  Always great advice.   Popped off the stem, put the watch in the press and the crystal, movement and case back came right out with just a little bit of pressure.  

And it looks as if it’s been many years since it’s been out.  

[Geotex]

Bulova also had watches with this style case so they also sold their version of a press. These purpose-made tools are nice, but as you found out you can find other ways to push them apart and together. 

My advice is to be careful with the crystal on these - they have a unique side wall geometry (as shown on the patent diagram above) and are not that easy to replace. Some NOS crystals are out there, and there are some ways to bodge other crystals to work (you can search for some other threads here on WRT) but it's best to maintain what you have if it's not badly damaged. The "official" opening fixture has a wide clearance so the crystal isn't subjected to pressure when the case is popped apart, and the closing fixture very tightly conforms to the crystal so the pressure is evenly distributed during closing (see picture).

[Latetothegame]

Thanks for the info Geotex.  I did press it back in with my press and it went in without any issue so I may have dodged a bullet there.  The crystal is not in great shape.  It has a lot of micro cracks around the edge.  I ordered a PHD 25 (28.5 mm) crystal.  It seemed to be a good match in terms of shape and the diameter was spot on.  
I do have a bit of experience reshaping them if it’s not quite right.  We’ll see how that plays out.  The dial and the case were both sort of a mess but they cleaned up nicely so I’m hoping that I can get a new crystal to fit (see pic).  Thanks again.  

[Latetothegame]

Here’s a couple pics showing how rough the case and crystal were.  

[Latetothegame]

So the PHD 25 28.5 mm crystal did not work due to the custom shape of the crystals used in the Benrus waterproof models from this period.  Luckily, I kept looking and was able to find the exact Benrus NOS 28.5 crystal that was used in the 3 Star.  A perfect fit!  See pics. 

[Nucejoe]

On 6/30/2024 at 1:05 PM, RichardHarris123 said:

If it is a split stem, you could try the compressed air method. 

 Oh man, I was under the impression that compressed air method works only if the case is airtight. If its got holes/ gaps it would fart from every hole.        and quite embaressing.

[Nucejoe]

 RoAmer put bumper automatic movement in similar case, what type of movement is in this benrus? 

 

[spectre6000]

I just picked up almost this exact watch as a 404. No crown, and needs one of those PITA crystals. I experienced the case type a while back with a... Certina? and recognized it before I got too busy trying to pry it open like some previous owner did. Fortunately, they were foiled, as the guts of her are pristine.

Replacing crystals on these sucks big time. You have to match OD, like usual, but also ID, profile, and shoulder height. With the Certina(?), I was able to get ID, profile, and shoulder height, but had to reduce the OD by hand. I borkulated the hair spring, so no telling how it would have held up... Those were early days in my watchmaking adventures.

Edited July 25, 2024 by spectre6000

[Geotex]

On 7/24/2024 at 10:29 PM, Nucejoe said:

 RoAmer put bumper automatic movement in similar case, what type of movement is in this benrus? 

 

The autos that I've seen in this type of Benrus case have primarily used the Benrus CF1 movement, which is an ETA 1256 as shown on 17jewels.info:

https://17jewels.info/movements/e/eta/eta-1256/

[Nucejoe]

Just now, Geotex said:

The autos that I've seen in this type of Benrus case have primarily used the Benrus CF1 movement, which is an ETA 1256 as shown on 17jewels.info:

https://17jewels.info/movements/e/eta/eta-1256/

 Bumper automatic in RoAmer is collectable for its unique design, perhaps the smallest bumper automatic at the time, but practically won't hold much power due to it's small barrel and mainspring.

Rgds

[spectre6000]

17 hours ago, Geotex said:

The autos that I've seen in this type of Benrus case have primarily used the Benrus CF1 movement, which is an ETA 1256 as shown on 17jewels.info:

https://17jewels.info/movements/e/eta/eta-1256/

This is what's in mine.

[Latetothegame]

Sorry, just saw this question about the movement.  The movement was identified as a Benrus model FE 255.