M-40 155mm SPG. Roco HO.
A little bit of a cheat here, most of these old Roco's come partially assembled, where you add accessories and paint. The M40 had a 155mm gun built on a modified late Sherman chassis. Used at the end of WW 2 and in the Korean war.
I had had one of these as a kid, my fathers cousins husband collected them, mostly German vehicles, this was out of place so he gave it to me. I found this one on ebay.