I am going through the different versions of the small fin cylinders, the termination years am I not 100% certain about as I think they could be fitted on commercial outfits and that kind of economy stuff even later on. 

Easy to recognize is the 101 cylinders with their threaded exhaust spigots.

1932~35 Standard Scouts and Pony/Jr Scout has the exhaust pipe slid into the spigot casting. 45ci also have number 27-E-43 cast on the base of one only of the cylinders for all that I know, front or rear, I don't remember...and they also got a 1/8" larger intake nipple outer diameter at 1.5" and consequently slightly larger intake manifold. I don't know if that was implemented in -32, or perhaps with the new Sport Scout in -33...

101, Standard Scout, Pony/Jr.Scout and the first years of the Sport Scout has a T-shaped intake, 1935 (unannounced in late -34) came the Y shaped intake for the SS, still the outside dimensions of the fins was small and similar to the earlier cylinders but the number of fins were increased with one more fin.. 

There is 2 versions of those, one (1934-37) with the exhaust tube inserted in the spigot and number 35-E-319 and 35-E-320 cast into the bases. The other (1938-39) has numbers 92859 and 92860 cast on the bases and the exhaust slip outside of the spigot.

To make identification of small fin cylinders a bit more muddy, there is the 1926-27 Scout cylinders. They have unthreaded spigots and the exhaust tube slip over, similar to the rare 1938-39 cylinders. I am not certain when exhaust nuts were implemented, but I suspect that came in 1928 both for 37 and 45ci. 

All 37ci and 30.50 Pony/Jr Scout cylinders count one fin less than the 45ci Scout versions prior to the Y motors.

1940 came the Scout big fin cylinders also with Y-shaped intake. 741 has similar big size fins but T-shaped intake.

Corrections, facts and opinions are as always very welcome.