The main gun seems to be 'inspired' by the 75-mm-KwK 42 L/70 of the Panzerkampfwagen V Panther. ;D
Yeah....it does look like that but I was going to go with the 75mm cannon on the M18 Hellcat tank destroyer.
Anyway, back to BT. :)
Well, since its a Militia tank, maybe say it started out as a rebuilt tank salvaged from other half destroyed tanks. Techs on some planet get to tinkering with some old cast off tank chassis and left over weapons. Seeing the need for a cheap and multi-role design, the techs combined the best assets of the tanks that they knew of.
The Vedette's main gun, the Bulldog's SRM's and mg's and the LRM ranks from a couple of Rommel/Pattons that were past their prime. This tank then had to fight during yet another surprise pirate raid and proved itself quite useful. Of course, this got the brass involved and after sending the basic design specs out, this more standerdized design came into being with the Original version now sitting in a museum for the masses to look at.