I had one in the shop recently like that and the same question crossed my mind.
I've been sending out triggers (JUST TRIGGER BLADES) for a long time getting gold plated, but have since dispensed with doing that. Now I am having many parts for the Perazzi's and P/W reloaders TiN coated both for hardness and wearability.
I really like the TiN trigger blades in a matte finish becasue your finger wails to slip, AND the TiN outlasts the gold 1000:1. However, if you ever plan to play with resetting trigger pull weight, you'd want to do that before you TiN plate it. The TiN is just too hard a coating to mess with.
I am now experimenting with the TiN process on the trigger "trees."
I guess I mis-spoke because I was thinking you were talking about the JUST trigger BLADE. I had a blade removed from a trigger assembly stamped "STA." It was NOT gold or TiN plated, but I had it TiN plated in the end.
I have also had some complete assemblies just like the one Rich directed us to on GunsAmerica. In my opinion, TiN plating an entire assembly is done purely through pure laziness. The one here at the shop was plated with the entire trigger assembly intact; spring, pins, etc. As I disassembled it, I noticed that even the pins showed signs of pating and but NOT plated where the pins, springs, and other parts were left in place during the process.
That, to me anyway, is about as dumb a thing anyone could do. The LEAST one could do would be to disassemble it prior to TiN plating.
I wouldn't pay a dollar for one that came in this condition, and I'd recommend the same to anyone else, for if you do, I wouldn't expect and "good" gunsmith to work on it.
I don't know anything about the one for sale on GA.
My thread was stating the fact that throwing a complete trigger into a bath of TiN is a dumb thing to do.
I think the "STA" you are talking about is a name for someone who worked on the trigger itself, such as installing new sears, hammers, setting pull, etc. In the photo below, the tor-right trigger shows a serial number (unusual to show more than 2 digits), and this is where the "STA" was stamped on the custome's blade.
The one trigger I had here in the shop had an "STA" stamped on the side of the TRIGGER BLADE, no where else. Many times trigger parts carry the entire serial number of the receiver on the front of the trigger HOUSING, and each part may or may not have a 2-digit number, representing the last 2 digits of the serial number, stamped on most all the larger parts. This is done at the factory in Italy to keep all the parts to a particular trigger identifiable to make reassembly easier once the parts return from the blue tank.
You have to imagine that at the Bresica factory they are working on many, many triggers at one time. Numbering would make it easier to place each parts with the balance of the same trigger's parts.