Its still easy to check if its a 550 board - the stock CC board has a 16 Mhz MC68030, and IIRC, looks slightly like an LCII motherboard (which makes sense, since its based on the LCII). The 550, on the other hand, has an extended LC PDS slot, and a 72 pin SIMM slot instead of 2 30 pin SIMM slots, and shares its design with the LCIII.

Either way, thats a curious find...never heard of a CC with a 4.5V battery before.