Not sure that any 239s were ever made in Germany.
A lot of folks extoll the larger sigs with the stamped sheet metal slides made in Germany as superior to the newer jobs with milled stainless steel slides.
Except for weighing an ounce or two less, there is no practical difference. But the difference does give rise to a lot on internet chatter.
You have a very good gun. Unless you win a large lottery, you will not be able to wear it out by shooting. If you put a lot of holster/handling wear on it. Have someone beadblast the slide so you get the full stainless effect and spray the frame with Duracote or such and bake it in the oven for a new gun.