Looks like it's possibly a mismatched Mauser Luger. Better pics of both sides, top and close up of all numbers. Mauser used the code byf during world war 2, around 1941. If this Luger was made in 1921 I believe the only company at the time making Lugers was DWM, and should have their stamp on it, although I can't find anything to show DWM was making Lugers that were date stamped in 1921. Not saying they didn't, I just can't find anything about a date stamped 1921 Luger from DWM.
Here is the company that made this display:
American Historical foundation
Basically their business is to gussy up a gun and get big bucks for it. As for your Luger, let's look at this from a couple of different perspectives.
1. The commemorative display: As an American if I was going to have a commemorative handgun that would remind me of our sacrifice during WW2 it wouldn't be a Luger. It would be the 1911. So why the Luger? You said your wife bought it 30 yrs ago (circa 1988). Can't speak for 1911 prices, but Luger prices were pretty cheap. This company spits out a commemorative gun for any little thing that happens and probably wanted to make a quick buck off of the memory of WW2, so rather than use a more expensive 1911 they used either any Luger they could get their hands on or they hobbled one together from whatever parts they could find. The general public, and probably even a lot of WW2 veterans wouldn't know what toggle would be on a 1921 Luger, so ignorance is bliss.
2. The Luger pistol: From a collector's standpoint this gun has very little true value. Because of the mismatched toggle (and not even knowing if any other numbers match the frame) this gun is considered "shooter" grade. That's provided the barrel is in good condition and the gun functions properly. Lugers were hand fitted in the factory, so a different toggle on a Luger would need to be checked out to make sure it would function properly and safely. The gun looks like it's as you said (salt) blued, rather than rust blued. The trigger, magazine release, take down lever and safety are most likely coated with with 24k gold. There are some shooter grade Lugers that are still displayable, however as a collector this wouldn't be anything I would want to display. My personal estimate on this gun's value is around $600-$800, provided the gun functions and the barrel is in good condition. The magazine is probably made by Mec-Gar.
I know it probably hurts to spend a lot of money on something only to find out it really isn't worth what was spent on it, but as someone that doesn't have anything invested in this (monetarily or emotionally) I would take the gun out of the case, and use it as a shooter luger and see if the case could be used for something else.