Is there a shoulder stock?
mattttt25 said:
Also, is there anything illegal with owning a gun of this type?
This is a rather broad question, but I'll mention one thing in particular.
A Luger pistol together with a shoulder stock is considered to be a Short Barreled Rifle (SBR) under the National Firearms Act of 1934 (NFA), unless it's one of a handful of specifically exempted pistol and
correct original shoulder stock combinations listed in the
ATF Curio or Relic List (Section III, pp. 35-36).
Possession of an unregistered NFA weapon is a serious federal crime and may be illegal under state law as well, although I'm not familiar with MD law in this regard. If this is what you have, I recommend quietly dropping off the Internet and hiring a good lawyer.
That said, please note that I wrote "
together with a shoulder stock" in my opening paragraph. Contrary to decades-old misinformation, it is NOT against the law to possess a Luger pistol that is
merely capable of accepting a shoulder stock, which is a Good Thing, because all (or nearly all) Lugers were manufactured with a stock lug; it's the double-slot thingy on the back of the grip.

Unfortunately, back in the day before many people understood the NFA (i.e. generally prior to the 1980s), this misinformation prompted many Luger owners to have the stock lug ground off "to make it legal", thus ruining the collector value of their pistol to some degree, for no good reason.

It is also NOT against the law to merely OWN a Luger shoulder stock, including a reproduction.
The trouble starts when the pistol and a (non-exempt) stock are together, even if they're not actually attached to each other, or if you possess both items with the INTENT to put them together. Intent is a legal grey area that depends largely on case law. The safest course of action, and the one I would recommend, is NOT to possess a non-exempt shoulder stock at all, unless you intend to go through the NFA registration and approval process (which is a whole 'nuther can of worms).
Mandatory disclaimer: I am not an attorney, nor do I play one on TV.
This is not legal advice. Caveat emptor and YMMV.