1st Luger....Help

[Tim]

Hi, need some help on this,i know absolutely nothing about Lugers. I just purchased a DWM(marked on cocking piece) Luger all matching parts except mag , dated 1911 (on slide behind barrel), serial#84xx, about 75% condition finish,on the front strap(not sure if that's what it is called(area from below trigger guard to mag well)it is marked 19.T.S.3.178. what is the meaning of these markings? what type of mag should it have? it has an aluminum based one with a waffenampt. i picked up this and a P-38 AC42 all matching from a friend of mine for $800 , the story is his father brought them back after the war. Did i get burned?As always an after thought of an impulse purchase....they were going to the pawn shop in the morning so it was now or never.His brother got a Broomhandle mauser ou of the estate, and it is going to be for sale also. i know this is a luger forum but it is Geman , what is it worth? Thanks in advance fo the information. Tim