Takahashi 2" Visual Backs to fit FS60C

[pmlogg]

I have a 2nd hand FS60C which came with a 2" visual back but it is not a compression ring version. It didn't come with a box to tell me the part number.

I see that there is such a thing as a compression ring version but I cannot tell from the price lists whether it is the TKA21110 or the TKA35110. I've also found listings for a TKP35110 and TKP35110 but have been unable to find out what the difference is between the 4. Any advice would be welcome.

Thanks

[pmlogg]

I should have said TKP21110 and TKP35110. Sorry