Looks like a planetary gear system.

Difference is the drive shaft will be center line rather than offset in a planetary system.

The main disadvantage of palnetary (for tanks) is a relatively low gear ratio, maybe 3:1 to 6:1 depending on how many stages (adds in length).

For the one pictured, looks like it could not habe more than 2 stages in the can.

The T55 has a higher top speed than WWII tanks so the ratio might be OK for this application.

Can't beat the sealed gearbox option, a great solution for an already space cramped model!

The standard T55 Hooden motors has near 32 mph scale speed with plastic tracks.