Well, the German "line" panzers - III and IV - went through quite a lot of upgrading through the war to keep them battleworthy. The late-war versions were something like ten-twenty tons heavier than the first models, mostly from added armour.

The German tank force at the start of the war was really pretty meh, all things considered. It wasn't for nothing that the senior commanders were getting ulcers at the very thought of having to take on the French, who had rather more rather better machines.