870 Trap guns: How do you identify?

[quickpointer]

I'm looking for a trap gun remington 870..
Seems like they made at least a TA, TB, and TC in 870.
How do I identify the gun that I'm looking at?

T is for trap and the other letter designates the grade of stock wood used.
After that I'm lost.

Thanks Quickpointer

 

[bobeyerite]

I don't own one but I have seen quite a few on the trap range. And they all have a gold and black shield on the side of the reciever.

 

[akr]

The drop of the stock will be more parallel to the rest of the gun. It won't have as much drop.