? on vintage AR

[Jafo]

I have the oppertunity to buy a vintage Colt AR (semi auto)
Ser# 59XXX The rifle is is nice shape and very clean. It has 1/12 barrel twist no fence around the mag release, no shell defelector or dust cover.
The front triangle hand guard was replaced with the round style. I know that can be replaced no big deal. The plastic is black not green.
The asking price is $1,100.00. So what is a vintage Colt AR value? I know the hand guard will detract from the value a little bit, how much? How hard are these vintage rifles to come buy?
This is a private deal between a friend and I. It is not on the open market. I already have four AR style rifles, none stock! I would like to add this to the collection and keep it stock.

[shiva]

Sounds like a deal to me. any SP1 in great shape wouldn't last long at that price.

ETA: From the serial number looks like it was made in 1977

[Jafo]

Thanks for the reply! The current owner thought mid to late 70'S as well.