Force Recon & MEUSOC guys had continuously using 45ACP 1911 since mid-1980s when the rest of the regular US military units starting turned in old slabsides. The problem was that those MEUSOC pistols, equivalent to the custom shop pistols in the civilian world, were built by a small team of skilled pistolsmiths in PWS Quantico. Too time consuming and not enough quantity to fulfill the needs. Toward the end of the program, the old WWII USGI frames that suitable to sustain high round counts those units went through were depleting quickly. Some few hundreds of new Caspian frames and some Springfield Custom Carry 1911 were procured. Even Kimber were awarded Interim ICQB contract as stop gap measure, which also failed miserably as Kimber ICQB pistols were quickly retired from services within years. At the same time, Marines want to prioritize their PWS shop gunsmiths to rifle program.
These factors somewhat lead to the new solicitation of new pistol trail to replace former in-house MEUSOC pistol program. There was rumor that William Keys, Colt President/CEO at the time, a retired USMC Lt. General, also push hard for the replacement program as his legacy at Colt. Colt did make a big marketing effort when it got awarded the new M45A1 contract touting the return of 1911 to elite military groups.
One big issue with the M45A1 was the original Cerakote finish looked like trash in the hands of these elite units. Colt went back and proposed change to Ionbond finish and provide a few refinished pistols to the Marines for testing. Unfortunately, at that time Marines had decided the fate of the M45A1 program (probably more on the budget issue than the pistols itself). Certain units continue to retained issued M45A1 until later days, but the rest were returned to Colt (both issued and unissued). Colt put big X on USMC slide marking and auctioned off those on gunbroker. At the beginning, people were skeptical about the authenticity of those auctioned pistols. Some early batch sold for very reasonable price. When those people getting these real deals started reporting the genuine USMC procured pistols were up for grab, price shoot up instantly and had climbing even more over the years.