1900's were not normally made in anything besides 7.65mm - the 1906 was both calibers, but not the 1900.

It looks like a 7.65mm and would bet a nickle on it being that caliber. as said above, see FAQ (but if a normal #2 pencil fits easily, its a 9mm, a bit tight, its a 30 luger)

also - I didn't think 1900 - commercial grips were numbered....

Ed, some 1900 grips were numbered (at least 15191 is), but I have no idea when the practice started.
Lyn

The photo of the inside of your current "custom" side plate is cut like an original M1900 type (different from the PO8), the outside is definatly unique. TH

The machining of the inside suggests to me that it is an original side plate that has been ground flat on the outside with an added piece, perhaps hard soldered onto the original.

KFS

No.2 pencil test tells me it a 7.65, guess I have 250 rounds of 9mm Luger ammo to sell.☺️
Thx for the FAQ tip fellows.

Larry.

that would be one explanation but begs the question...Why?

More and better images of the side plate are needed to help solve this mystery.

here are my best close ups.

Those help. Here's some lightened versions.
Whoever made that side plate had skills and the proper tools.

thank you for brightening up the images, will save this to my Luger album.

Reading Karl’s post again and the thought occurred to me if in fact the face of the side plate contained a original number but was ground away is it possible the gunsmith restamped the number we see on the inside in order to assure to future owners it’s an original part!
Just fishing for answers here.

Ragnar,
It is not an "original" part, may have started life as one- but is no longer.
There is just no "explaining" the why it is the way it looks- and it really doesn't matter -
Someone modified it, or created a new one.

Accept it for what it is and move on! JMHO :)

03man
Of course your right but just love solving a good mystery if I can lol.
Guess it should be enough knowing it’s a M1900.....if in fact it is.
Would love to know the year of manufacture if anyone cares to throw out a guess.

It is definitely a 1900, more properly called "Old Model Parabellum"; I think someone already suggested 1901 as its mfg. time, but that may be on the other forum.

Wish to thank all here on the forum for their help,advice and expertise.

Larry.

Nah, that just means you have to get another in 9 mm!

Hmmm’!