Originally Posted by
noobinsf
There is this example on the interwebs of a 1986 Olympic with top-mount levers and a Light Action derailleur. The person who posted claims it was from the original owner and had only been ridden a handful of times. Shifters look to be index, but hard to definitively tell.
Damien B?s 1986 Nishiki Olympic | Old Ten Speed Gallery
Other samples in my database show a Light Action friction lever set. The other concern is the rear derailleur, which is the L523 version. In 1986 the only Light Action derailleur which was listed as being SIS compatible was the L525-SS. SIS compatibility is not mentioned for the L523. Clearly, it was designed for SIS compatibility, as later versions are rated as SIS compatible. However, the 1986 version is not listed as featuring the Centeron pulley, which would have been critical to proper indexing. I'm wondering if Shimano was penny pinching on the L523 until they got feedback on the popularity of SIS at the entry price range, via the L525-SS? So, while the 1986 Nishiki Olympic may not have been SIS compatible, it would have been easily upgraded. This would explain the aftermarket New 600EX SIS levers on the OP's bicycle.