D6B serial number plate missing

I bought a Caterpillar D6 or D6B. The only serial number I can find is on a plate attached to the engine (44A2457). The ID plate on the rear is missing. The rivets are still there, but no plate. Is the machine serial number stamped stamped anywhere on the rear? If so, I guess I need to do some careful wire brushing to remove rust and old paint. I feel like the engine may have been swapped because there are some controls on the dash that don't connect to the engine. Two pull handles on the dash operate some rods and levers on the engine side of the firewall, but they don't connect to anything.[attachment=51980]PC291493.resized.jpg[/attachment][attachment=51981]PC291494.resized.jpg[/attachment][attachment=51979]PC291492.resized.jpg[/attachment][attachment=51982]PC291496.resized.jpg[/attachment]

Hi, hdonly.
The serial # should also be stamped into the metal under where the tag was located. Some 'delicate' paint removal may be required.

Just my 0.02.

The unused rods are most likely controls for the in seat 12v starting system for the pony motor.

I figured that was what the unused controls were for. I am curious if the engine was changed or just converted to straight electric start. There are no glow plugs on the engine but it does have a compression release that is disconnected. It needs a small shot of ether to start it. Once warm, it will start very well without the ether.