72v1 CONSTRUCTION OF WEIGHTS

[Searcher]

If there was an attempt to draw a rocker with an arrow and  trunnion in mutually perpendicular planes, then there is no hint of an axis passing through two ears of trunnion on which the rocker should rock.
This can only happen if the artist has never seen the scales (copied from another source) and he raised the ear of the trunnion too high (above the rocker).

Vladimir, this is how I see the construction of the VMs scales (Libra):
   
Likely, the left joint in the VMs Libra is just incorrectly too high, maybe it just was drawn without needed accuracy.

[Koen G]

I'm posting this image as a possible parallel for the way the scales are attached. The mosaic  from Sousse (Tunis) shows workers weighing metals from a ship's cargo. What drew my attention was the thick crossbar from which thinner parts protrude at the end. I don't know if these are attached separately, or a metal bar runs across the whole length for reinforcement.

   

[-JKP-]

I like that one, Koen.

I've searched for years, collected hundreds (not just zodiac scales, but all kinds of scales) and I have found very few that have attachment points similar to the VMS. I do have a few that have upturned hooks, but I would have to look to see how many.

...
I'm back (I took a look). I found 8 with upturned hooks, but only one (Immerwährender Kalender Libr. pict. A 92) that looks like the hook might be a separate part or separate material from the supporting bar.

So... your example is a rare instance and a very interesting one. A separate extended bar is the kind of detail someone perpetrating a hoax would be unlikely to include in a drawing unless they were copying from an exemplar, and the odds of there being an exemplar with this specific construction appear (at this point) to be low.