Is a Remington 1100 Synthetic 20 gauge Made on the 12 gauge frame or the the 28 Gauge frame ?

Would a 21 inch Barrel be for it be hard to find or expensive ?

The reason I ask is I have been talking to a guy that has one and he says it is a LT-20 but he also tells me that it does NOT have LT-20 on the side of the Receiver.
It has a 26 inch vent rib barrel with rem chokes.

If it is on a 12 Gauge Frame is it worth as much as if it were on a 28 Gauge Frame ?
It has been Cerracoated in a Bronze color,does that hurt the Value of the gun?

I need to know before I spend Money to buy it.

Thanks

It's an LT 20. The standard 20s were long gone before matte finishes and plastic stocks. I don't remember when they stopped using the LT label.

Thanks Virginian