West Germany Brd 1 Pfennig 1950 J - Different Material? From The 5 PF?

A regular 1 Pfennig is made of copper clad steel and should thus be red to deep brown - just as copper colorizes over time and when used.

The 5 Pfennig coin was made of brass plated steel and is thus very yellow/golden in its shine. I can't see what your coin actually is made of, as both the pictures and my screen (and especially the combination) aren't good enough.

You can check if the coin is actually just plain steel, lacking the copper plating. My screen and the pics (especially the combination of both) aren't good enough for me to determine. It's really a shame about the gum spot, as it's really a nice coin otherwise. I am not familiar with this variety of error (if it's indeed an error), but I can tell you that, especially right after the Second World War, a lot of coins with errors have been struck for the Bundesrepublik and 1950 wasn't an exception to the rule.