Was a calibre 85 ever used on a Big Eye (884100)?

Like any UG aficionado I'm always looking at UG watches that I'd like to potentially own, especially from their complications line and the reference 884100 Big Eye is one such model.

Recently, in speaking to potential sellers, I've come across 2 different 884100/01 (i.e. the reverse panda variants) where the movement is stamped 85 instead of the expected 125. Initially I dismissed these as being incorrect or replaced part, but then someone commented that calibre 84 (not 85) was used in the later run of the watches. There isn't too much scholarship that I've found about the Big Eye (except @subregister's exceptional work on documenting the details of the panda variant (here for those looking) and even that specifies 125 as the correct model (assuming only the dial was different between these 2 models).

However, there are 2 things that seem to hint at the possibility of the 85 being potentially acceptable as well:

1 - This page which lists UG calibre's seem to indicate that that like the 125, the 84 (not 85 as in this case) was also a modified Valjoux 23. It also shows calibre 85, but as a modified Valjoux 72 instead of 23.
2 - This discussion on Omegaforums about a Spacecompax where the UG big Eye and 84 (not 85) being part of later Big eye's (from 65 apparently, since the Big eye only ran for a couple of years) is discussed including @Diabolik stating that its likely the bridge (and not the movement itself) was replaced since both Valjoux calibre's had interchangeable parts.

I would love to know what the experts think. Here is the picture of the UG where I first saw this anomaly.

I've since found out (or rather, learned) that the bridge with 85 was used in the Nina (and possibly the Evil Nina). Could these perhaps be replacement parts (that are interchangeable with the Big Eye as part of a service or fix) or more UG idiosyncrasies related to assembling watches with whatever parts were available at the time. Like I've said, recently seen 2 of these surface.

Maybe it's just a frankenwatch, my friend. As you correctly said, 125 is the UG name for Valjoux 23 movement (2 counters). Valjoux 72 is UG 85, so for sure this bridge is not correct with movement and watch reference.

I have seen in my past research online more than 5 big eye with a cal 84 inside (v23).

No, it was not. The caliber 84 was ...

Caliber 130 is based on early Valjoux 72 Brequet (also used on daytona). It is found on very early 60s Compax references (the 2270[1-6] references with dauphne hands, nina, evil and early aero compax references)
Caliber 85 as above but later version of Valjoux 72 (go through forum and you will find a write up on differences between 130 and 85)

Caliber 125 is based on Valjoux 23 brequet was used on the early 60s big eye and Uni-Compax such as the 32601-1 (and so on)
Caliber 84 as above (based on the later Valjoux 23) was used on the later big eye references

The illusive Compax 22706-1 (130 caliber - Valjoux 72 brequet) with applied indexes and logo. Rarer than hens teeth !



the 32601-1 (125 caliber - valjoux 23 brequet)

Thanks @Diabolik, all clear.

It seems these 2 that have popped up recently in quick succession may be using replacement parts, though I wouldn't strictly speaking refer to them as "Franken's" because almost everything else is intact. I'll try to post a picture of the other Big Eye that was recently put up for sale with an 84 bridge.

Btw that 32601-1 has been posted for sale at craft and tailored for a very compelling price, but from what I can tell, and is not super clear from the pics, the calibre no on the bridge isn't 125 but something else....from what I can tell either a 140 or 149...)

Could be. I did not check. However, unlikely. I have not heard of a 140 or 149. Just for clarity and completeness, the Val 23 and 72 are almost identical. the 72 has an extra wheel. The bridge is common. That's all ...

For info on the valjoux 23 and 72 try this ...

https://reference.grail-watch.com/family/valjoux-72/

The early Valjoux caliber 125 and 130, were superior in many respects (comparable to the daytona V72). Tolerances and build quality was of a higher standard. Therefore, having the original movement , does make a difference on a vintage. When buying, it is something I would look at and a key factor in determining value and desirability.

Thank you, you've answered many fundamental aspects of my question and addressed the ultimate purpose behind creating this thread - to gauge collector sentiment on how a replaced part, which is signed UG but has a different, incorrect caliber reference number, affects the desirability/collectibility of a vintage UG.

My view is that if these parts were common or similar between identical reference then even if an incorrect (but original) part is used, given the scarcity of this particular reference, it may be considered acceptable (though less optimal) than one that has a non-signed part (or worse a movement that does not function due to this part being faulty). Again, not ideal but understandable, in my view.

As promised, here is the other piece that I came across with a movement part signed 85. The dial is very clean (and almost identical to the one above) but I assure you its a different watch altogether.