We're not sure we've seen cleaner Boss pedals here in the shop than this Boss CS-3 Compression Sustainer (along with some other Boss pedals from the same collection).
As far as modern compressors go, the CS-3's inclusion of a tone control changed the way the effect was used still today. You can dial in anything from a subtle "grab" to a more dramatic squash, all while having control of the clarity of the compressed signal. It's another example of Boss's ability to deliver an intuitive and toneful effect right out of the gate!
This one's in Mint condition with the original box. It looks borderline NOS.