The Lugers made by DWM, Erfurt, Simson, Mauser, Krieghoff, Bern Arsenal (Spandau, Vickers ?) are the real deal. Still, you might buy one that works well, or is a stinker needing a lot of work and parts to shoot reliably.
There are mixed reviews on the Mauser Parabellums made from about 1970-1986. I like them. Mine looks good and is a nice shooter. Some say they are poorly made and inferior quality.
My friendly advice is don't buy any stainless steel Luger. If you do, chances are good that you will regret buying.
More advice, if you want a nice Luger that you can shoot, and is the real deal, take your time looking and buy a WW II era Mauser Luger. If money is no concern buy a nice condition matching number Luger for probably $1500-2500 or more. If money is a concern buy a nice condition non-matching number Mauser Luger for probably $800-1200, and you'll have an interesting piece of history that will look good, shoot, and be the real thing.