Howdy
I would say that you have a MKII. The frame is probably an Essex or a Foster. The factory papers that i have indicate that your gun was probably made in 1979. The "D" prefix started with 7199 and was used to indicate a different frame contractor for ATF purposes. As to the value, probably around $5-600 depending on what you have with it. Original Detonics paper work and boxes seem to sell pretty good on there own. Factory mags are fairly valuable. I haven't seen that many MKIIs around. The quality of these pistols in my opinion is VERY high. I've owned MANY 1911 style guns and built even more for customers in law and personal protection and can say that there are few if any factory guns that can duplicate the quality ofthe Detonics pistols. Some Kimbers are as good or better but you really pay for it. I've fired 1000s of rounds in most of my Detonics guns and only ever had one traumatic failure. A recoil spring broke and then the end of the slide cracked. I was fireing Corbon HOT 230gr ammo in a tactical drill and the gun never stopped working. I didn't even know it broke until I cleaned that night. I really don't think you buy anything even close to these guns for the same money. You can find NIB Combatmasters for around $8-900 and you would be hard pressed to find that quality and hand fitting in a new gun for under $1000. Hope this helps!
L8r
Conley Janssen
USMC 87-93