Please post some pictures. The "two-tone" finish seems highly suspicious, but it's always hard to comment on the originality of a pistol's finish without pictures.
I do know that it is WWII era because the serial number dates it to either 1943 or 1944.
FWIW all WWII and earlier PP's have slide legends reading "Zella-Mehlis (Thur)" rather than "Ulm/Do" ("Thur" refers to the German state of Thuringia, whereas "Do" refers to the Alb-Donau district of Baden-Württemberg). The original factory wound up on the wrong side of the Iron Curtain when Germany was partitioned after the war, so the company had to relocate.
WWII-era PP's should either display military Waffenamt "WaA" stamps or commercial eagle-over-"N" proofs around the trigger guard, but these markings are subtle and may have been obscured by a heavy-handed amateur refinishing job.
BTW is the pistol .32ACP (7.65), .380ACP (9mm Kurz, may be marked "9M/M" or simply "9"), or .22LR?