Can anyone tell what model Melos this amp is?

Melos made that amp as stereo and as foca said as mono blocks.  It was a 200 as stereo and 400 as mono blocks (also as 400 Gold).

I also had a pair that I bought from Chesky Records back in the early 90's.  I had mine upgraded by an ex-employee in Las Vegas after Melos closed.

I both one pair of these vintage for more then 18 yeras ...they are fantastic ...if you need the "owner Manual " i willsend to you .....

V1   12AX7 OR ECC 83
V2    12AU7 OR ECC82
V 3, 4, 5  6  6KG6A OR EL 509,EL 519

hi, can you tell me what tubes are inside ,

I can't answer your question, but fwiw, the former owners of Melos, George Bischoff and Mark Porzilli are now the brains behind The Memory Player, at novaphysicsgroup.com. The Nova web site is truly bizarre, but the Memory Player is truly an amazing product -- I've heard it and what they say is true. Mark Porzilli is also the designer of Scaena loudspeaker -- a genius imho. Anyway, you may be able to get more information via the Nova Physics Group.

Just an observation as a Melos owner: model numbers mean little with Melos. Most all Melos pieces were always works in progress. Great stuff, though not the most reliable and very hard to get repaired now because schematics are virtually impossible to find. Check all solder joints.

a maestro, i think