As noted, your gun with the PCG serial prefix was part of the first run of the Mag Comp guns, and had a 6 shot cylinder. As noted, the run was for ~ 300 pieces. Product code as noted above.
The second run of these was made after (occurred in the 1996/97 timeframe), and had a product code of 170074. The difference was the serial number prefix, which was TPC, and this model had a 7 shot cylinder. This second run totaled 366 pieces.
Neat gun, your gun, if NIB, should be worth over $2k in this current market.
As to nomenclature, lots of descriptions abound, the first flyers from Lew Horton called the first run the Mag Comp, as noted it had a six shot cylinder and a front night sight.
The second run was called the Carry Comp or just 686 Comp in the brochures., and/or depending on who you talked to at Lew Horton.
This later gun was in the -4 config and had both front and rear night sights.
Here's a pic of the second version that I had in the collection... The flyer above shows Uncle Mikes rubber grips, but the early guns (this one s/n 13) came with Eagle Secret Service grips: