Vintage shimano chain ring part numbers I have several vintage NOS chain rings with part numbers. Is there a way to look them up to see what the specs are? Example: 
I have 4 rings with 24T, 68BCD: 


two of them have part# 17L24000 stamped 1G L-24
two of them have part# 4-1C424000 stamped M9 P-24.


Do these differ somehow?
The first is a Shimano M950 chainring:
https://si.shimano.com/pdfs/ev/EV-FC-M950-1591.pdf

The second is a Shimano M952 chainring:
https://si.shimano.com/pdfs/ev/EV-FC-M952-4-1757.pdf