I too have an old Sony, a TC-W230, it is a dual deck model but will
only record to one deck, the other is for playback only and this
normal/high speed dubs to the second deck, it does have manual volume
sliders and a front mounted headphone socket and is servo controlled.

As Sony seem to have made a number of this type of deck in the past
it might be worth looking at their site to see what they are doing
now, and also what they have done in the past if possible.

Hope this helps.

Cheers

Cattail !