Help with decoding.

[kx57]

Hi,

I have decoded the VIN on my old man's truck. No problem there.

The secondary number (see picture) that is FT055379 is giving me trouble. I can't seem to locate reliable information on what that means.

I'm assuming it's the trim package/colour info?

Anyone an expert on this that can enlighten me?

I gave it the old college try on research before posting, I don't want to waste anyone's time. I didn't see anything in the stickied FAQ talking about this...and the GM Heritage original spec PDF doesn't seem to show anything either. All the VIN Decoding pages I've been to either don't mention it or it doesn't match up.