That one wreck of a Solar 1 Engine of Phoenix Arizona, which is missing its proper base and is seriously filthy, does have one somewhat interesting feature. The pulley mounted between the flywheels is of a size and form I have never seen before. Likely home-made or aftermarket of some kind, but if original, that would be very interesting.
Another faint possibility is that it could actually be the remains of a Davies-Charlton Stirling from the Isle of Man UK, but it would take some careful measurements to make that determination.