The early 1977 pedals continue directly from the late 1976 Ram's Heads, with a bigger low end and a fuller fuzz tone. In fact, some of the earliest 1977 circuits are almost identical to the late 1976 versions.
As the circuit evolves through 1977 and into 1978, you begin to see capacitor changes that gradually pull back some of the low end while increasing the overall gain. Most of these pedals use BC239C transistors, although some can also be found with the higher gain MPSA18. Together, these changes show the gradual evolution of the circuit toward what would become the Reverse Logo Big Muff.