As I type this I'm looking at 7 different inserts. Three are for 7-speed and 4 are for 6-speed.
When Syncro I was introduced, the inserts were color coded black, red, white, yellow, and blue/green. Each color corresponded to a certain derailleur/freewheel/chain combination.
Things got a bit more simplified(yeah, whatever!
) with Syncro II. Each insert was stamped with a letter and a number, of which there were 3 types each for 6 and 7 speed combinations.
Six-speed:
Record,Super Record,Victory/Triomphe, and Croce D'Aune all used a 6V(yellow?)insert.
Chorus used either an A6(red) or B6(white) insert. I don't know the differentiation for these two
Seven-speed:
Record,Super Record,Victory/Triomphe, and Croce D'Aune all used a 7V(color?).
Chorus used either an A7(green) or B7(black), differentiation unknown.
For a while I used the B7 in combo with a Chorus derailleur/Regina America 7 freewheel/SRAM PC68 chain.
Shifting was satisfactory at best.
Then I switched out the Syncro for some plain old C-Record friction shifters and was more than pleased. Sometimes simpler is just better.