Rumors are that some were made of steel from the Graf Spee, .
Actually if that was the rack number it’s now the serial number, in the us the serial number has to be on the frame and since the main spring housing can be changed, the government wouldn’t allow that to be number for the gunActually, I think the 25471# is a rack number. The Serial number is the one on the mainspring housing. On the two I own neither has a number on the right side of the frame.
As for pricing un-rusted versions are currently priced 5-600$. There a B prefix (sold to the British) at RIA now listed at 11-1200$.
Here's a couple of good articles: https://www.guns.com/news/2013/08/19/the-ballester-molina-pistol-argentinas-almost-1911 https://www.shootingillustrated.com/articles/2019/10/17/classics-the-argentinian-ballester-molina/
Rumors are that some were made of steel from the Graf Spee, that the slide would ring when slide lock was released, because of the quality of the steel...well made guns, and beautiful too.
I remember hearing G. Gordon Liddy say that on his radio show many years back when somebody gifted Mrs Liddy (as he used to say ) one.
I don't believe this turned out to be true though.
On the B-M the mainspring housing is part of the frame...not removable. The lower is not like a 1911; only the upper is identical. You can tell in the pictures that the font of the numbers is different from the rest of those on the pistol.