Part of the mainly-export H/K lineups but the original version, A660, was Japan-only. Built by Shin Shirasuna, of course.
The A660 was silver-only and had only vertical LED dots to identify functions ; the PM660 changed the latter with written backlit descriptions and was available in silver or black depending on the destination market (and black in Japan).
Inside both versions, which are identical, is a very beefy EI trafo, a partly copper-all-over chassis (A660 only !), four rows of black-anodized sharfin heatsinks and a properly isolated phono stage.
Features-wise, this was before CD so there's an MM/MC selector and a four-way capacitance trim acting on both phono inputs ; phono 1 is MM, phono 2 is MM or MC. The "main direct" switch circumvents all but the volume pot and source selector but takes -7dB.
Healthy, reliabe and very powerful.
Nudies of a black PM660 here ; an A660 here.