Park 100-watt bass

This early '70s amp is marked "100-Bass" I would date it at around 1974, but it still doesn't have a circut board (Marshall switched over in the middle of 1973, I think). One other unusual thing is that although a 100-watter, it has no vent in the top. I traded a few guitars I never used for this one but ended up never using it live.

Left: Close up of back panel