This is the Apogee Components Saturn 1B that was modified to be a 3-stage rocket. The bottom stage has eight engines (4X A10-3T, 4X C6-0). The middle stage uses a C11-0, and the top stage uses a A10-3T. It appears that the C11-0 had a blow-through, because as soon as it ignited, it immediately ignited the upper stage. The top two stages have hidden fins that flip-out when the motors ignite. These flip-out fins performed flawlessly.