Is $800 a good price - yes, no, maybe.
In the past six months I have seen an original Leman sell for 175 bucks and an original Armstrong go for $125,000.
Since 800 is somewhere in the middle it might be a good deal.
Not trying to be silly here, just trying to illustrate that that's a pretty generic question that can have very diverse answers.
Is the rifle by a known maker? are you sure it's original? can it be shot? has it been checked out? etc etc.
If it really is original and it's "sound", shootable and serviceable and I had 800 bucks doing nothing and liked the rifle, I would buy it and shoot it.
I'm in the camp where "rifles are meant to be used", I can hang pictures and posters on the wall.
If it's safe to shoot, then shoot it. If it's value is "only" 800 bucks it's a "rifle", not a piece of collector art.