Single stage paint job.. no shine

BIG difference between “base coat” and “single stage”. I think we all agree with that. That withstanding, the test to differentiate between the two would go like this. Much like 1WildRT mentioned, find a inconspicuous area. I’m not sure the jams would be the best spot as they may not reflect what is on the outer body. The jambs may have been cleared already. Mind you, there is a clear basecoat and is often used with custom paints especially when more than one color is involved.

Slightly wet a white rag or paper towel with lacquer thinner and quickly wipe the chosen area. I’m thinking the bottom of the rocker panel. If it is base coat, it will immediately transfer color and probably discolor the area. Single stage will take more effort to transfer the color and be harder to dis-color. Again, it may have basecoat clear on it and may not transfer color immediately.

If that is the case wet it again and touch it with your finger really quickly. If it is base coat only, it should feel a little tacky. Single stage paint will hold up a little better and not be tacky with a quick wetting.

Make sure you figure out what you have before you take a buffer or sandpaper to it.
NOW technically, if you decide it is base coat CLEAR, you can lightly scuff it with #800 and clear it. If it is basecoat without clear, it needs to be sanded and more base coat color applied for proper adheasion of the subsequent clear coats.

Off the record. If you decide it is basecoat, I’ve often thought you could spray it all with a quality universal reducer and that would soften it up enough to warrant NOT sanding it and having to re-apply more color. You can not clear over sanded base coat without adding more color. This is definitely not an approved procedure and I have never done it. Best of wishes in your findings and decisions.