Looks just like one my old Amps I used back in the early 90s. It was a Really clean sounding amp.kinda thinking about picking it up to be honest. A little high on the asking price though\.This series were really pretty much bullet proof. I had a nice line of them at one time.
https://www.ebay.com/itm/Sony-XM-5540-Amplifier-4ch-old-school/153090600600?hash=item23a4e92e98%3Ag%3AyFMAAOSwxipbN99h&_sacat=18795&_nkw=old+school&_from=R40&rt=nc&_trksid=p2499334.m570.l1313.TR11.TRC2.A0.H0.Xold+school.TRS1.TSS0
https://www.ebay.com/itm/Sony-XM-5540-Amplifier-4ch-old-school/153090600600?hash=item23a4e92e98%3Ag%3AyFMAAOSwxipbN99h&_sacat=18795&_nkw=old+school&_from=R40&rt=nc&_trksid=p2499334.m570.l1313.TR11.TRC2.A0.H0.Xold+school.TRS1.TSS0