It "sounds" like a factory-custom Mark V. You could special order anything available.
http://www.sightm1911.com/lib/history/detonics.htm
What's certain is that it is not a Mark VII, a Mark I nor a IV. Probably not a II.
Fwiw, seems that the best functioning ones were the Bellevue with serial numbers over 20,000. By that time all the kinks were gone.
HTH