Here is a link to a picture of an T-54 or T-55 with an escape hatch on the bottom http://cdn1.fotopu.com/img/130976-3.jpg
So there were Soviet tanks with bottom escape hatches, my mistake.
But there is no putty hole or what so ever found yet.

First of all do not feel Yourself offended. I do not have seen any picture of Soviet tanks (or which tank at all, before) with a putty hole/escape hatch. I have read about rumors of bottom escape hatches on some German panzers (according to the rumors Panthers and Tigers). Thats all.
Besides that there is a picture of a hole in the bottom of a German tank with a rubber sealed circle shaped hatch at the bottom of a German tank. A hole witch could been a putty hole (in my humble opinion – regarding some French toilets – rather big). Or could it been an escape hatch.
If this is a putty hole, why on earth was no picture ever seen took in a Soviet, British, French or an USA tank with the same putty hole? Only the Germans have to shit during a tank-battle? Nobody else, just the Germans? Is there any veteran of the Panzerwaffe or the Waffen SS ever asked how they been excused while they fought the Battle of Kursk?
OK that hole could been used as a toilet if the need was very high, but primer it was an escape hatch as far I can judge. But I am open for any argument of course.