I've used some OEM factory quarts of enamel from the late 50's to touch up parts of a survivor still all factory paint car. I ran about a 50/50 chance of the quarts I got being usable - after letting them re-mix on a paint shaker for like an hour.
As far as value is concerned that can is probably worth more to a collector than the paint is to an automotive enthusiast. It's only real value is to someone with a Duco tinting system, which is probably non-existent. As noted it was intended to mix with metallic. If you try to use it as a clear coat it will put a yellow tint on the finish. If you try to spray it over an enamel it will probably lift or wrinkle the finish. To put it over a later acrylic lacquer, you would have to let the base coat dry, wet sand with 400 grit and then spray or you could have adhesion problems. I wouldn't even use it on wood as opposed to Varathane because it will turn to a peanut butter like finish in time. Interesting in terms of history, but there's a reason they quit using those finishes.
I don't want to confuse my advice to tinbender with his 50plus yr old nitrocellulose lacquer and the OP's 23 yr old acrylic enamel. If that enamel can be remixed without separation issues, my only concern would be to make sure that it's a gallon of mixed paint and not a gallon of red tinter called "Honduras Maroon". I've never used that tint system so I'm not sure, if there's a specific paint code listed on the can it should be a mixed product. A quick call to anyone that's familiar with the old PPG systems should clarify it. Next chore is to find the right hardener and reducer to go with it... that could be the deal breaker... without it the paint will never (yes I said NEVER) dry properly.
It's a great looking color, Honduras Maroon. Last driver of "Alley Oop", Bones Steavens being interviewed. Bob
My cousin used to work in a paint store in the 70's. He was always bringing home mis matched and old unsold paint. I eventually ended up with all of it, Lacquer, Acrylic enamel and some syntho. I've been using it for the last 40 years with no problems.
i've got all this old paint, the few cans i've opened look pretty good. i'll be trying them out when it gets warmer. i have about $10 invested in it all.
Hey, I'm diggin the "Rinish-Mason'' (RM), and the early Ditzler (PPG) cans & some of the old ACME. They remind me of very old friends
Hey, I just found 2 jars of pearl additive from the 70's in my shed. Still looks liquid and pearly.......