http://www.millerwelds.com/
This is millers site. I searched for d-50 but no match. Go there and search, you have more info about the machine than I. There are specs there for all current products (as pdf files). I believe there are manuals for even machines they no longer manufacture.
Bill
Jim: If it has a 14 pin connector is is a CC/CV machine and newer than 1988. The machine is rated at 350 amps 34 volts 100% duty cycle. Amperage range is 50-500 amps DC, CV is 14-38 volts. Engine is a Teledyne-Continental TMD-27 with 38 hp. Fuel capacity is 16 gallons and it weights 1650 without fuel about 1800 full of fuel. If you have any other questions please contact me.