The "little" ESOTEC, with two rows of red LEDs flashing aplenty.
Same basic structure as the Sm-6 power amp with its Heat-Pipe cooling system but smaller caps and a little less power in both Class A and Class B modes. Fair 2-gang blue ALPS volume pot (but not exceptional given the asked price).
Only the early units have the Marantz ESOTEC tag on the upper right of the front, gold in the USA, black in Europe ; later ones only have Pm-5 written.
Marantz had lost the name's © which had been registered by another company... but Marantz sold at least half a million Pm-5s so it worked nevertheless.
Available in Japan with a (welcome) wood-enclosure and also in an x-rare black version (post-ESOTEC) which was never advertised or shown anywhere.
Nudies aplenty here.