Betting it's a big heatsink that comes with the Keeping up with the Phils' BG-400. The combo is a C4 cab (four 5 inch drivers, front port) and a 500 watt @ 4 ohms amp. Since the C4 weighs in at 30 pounds, that means the amp alone is 10 pounds.
At 28 pounds, the PJB Session 77 Combo may be near-ballpark. Two 7 inch drivers, rear ported, and 100 watts. Only a Line Out and Headphone Out. My SWAG is an Elf combo is going to be a lot louder all 'round. Different tools.
Friendly bandmates who offer to help load-in a BG-400 without ever having seen one before will experience the opposite of
@biguglyman 's bandmates when they lifted is GK for the first time.
Were one to believe in karma, the physically diminutive PJB BG-400 might be seen as interest paid on unkind thoughts about hauling a Peavey combo.