Scott 2560 Used Before First Stay

I know it is not uncommon to find stamps used prior to the first day, especially in the 90's. Not my area, but came across one in a collection I purchased. This is #2560 used 8/20/91 in South Carolina. The first day ceremony was in Springfield, MA on 8/28/91.

My question is more about the cancel. Upstate, SC GMF 293 & 296. Upstate is a region in SC, not a city. Most of the zip codes in that area start 293 or 296. Guessing this is just some regional processing center? Apparently I just answered my own questions as I thought about it.

Correct. I believe it is the Greenville SC USPS Distribution Center which has been overwhelmed in the last few years as other Dist. Centers in the area have been closed and moved there (like Asheville NC).
Don

Edit:
Here is a spray cancel from this facility

Anyone know if there is a list of earliest pre-first day usage of stamps?

Early releases occur frequently. Linn's covered these quite regularly in this era. Here is their Sept 30, 1991 article with the 1991 year-to-date list including the basketball issue then known used as early as August 2.



Map from 1994 "National Five-Digit Zip Code and Post Office Directory" showing the sectional centers in South Carolina as close to 1991 as I have handy. The map agrees with the facer canceler impression shown by the original poster of the combined operations of the 293 and 296 zip areas at the GMF (General Mail Facility).