Portuguese m904/39 Vergueiro: floorplate follies

Sorry if this isn't the right forum for this. I'm new, and this thing has at least a little Mauser in it, so...

I recently purchased the rifle in the title and am having trouble understanding what, exactly, I got. It's got the right receiver markings, action, etc., but is mismatched and, most strangely, has a push-button floorplate. Everything I've read about these Vergueiros mentions a hinged one. The floorplate itself is almost impossible to detach or reattach--of course, it looks like someone took a punch to the release button... over and over. And it's got a strange "3" mark in addition to the typical two digit serial. I can't find anything like it in my references. So I'm interested in identifying just what set of parts I've actually ended up with, and I'm hoping the people who REALLY know what they're talking about can help.
I'd like your advice: what photos would help the most?

Thanks for your help folks. With any luck, I'll be able to start putting up photos tomorrow.

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As promised, the photos. Note the various numbers and the symbol on the floorplate--I just can't figure it out.

The curly backwards 3 is actually the Greek letter "Eta" as used on parts for the Brazil Mauser. No wonder the fit isn't too good!

I think it can fairly be described as a "bitsa".

Greek letters, of course. I'd never have guessed.
"Bitsa" sounds about right. It looks like FN used the Greek letter system on their Mausers. Any way to tell what year contract the bottom metal was for?

Many gunsmiths in the 50s, 60s and 70s would switch out the hinged floorplate on the 1904/39s for a standard Mauser floorplate. They would then use the hinged floorplate on the sporter Mauser they were making and resell the 1904/39 for the same price they paid for it. The reason is the hinged floorplates Mauser was selling was something like 10 or 15$ and buying a M1904/39 was about 10$. So for no cost they were getting a 10-15$ part for there sporters that they were selling.