I have what started out as a nice shiny aluminum coaster in my study. I made it from a piece of 1/4" aluminum left over from another project. I put a nice mirror finish on it, but it didn't take long for coffee cups and drink glasses to cover it with scratches that make the finish look horrible. (I'm staring at it right now.) Unfortunately, that's the nature of aluminum. Given that we intend to actually use them as coasters, I decided on a matte finish taken down to 400 grit with an orbital sander. Did that on the hot plates and wear and tear seem to blend in to the finish. Good suggestions, but I suspect they'd show unsightly signs of wear in a very short period of time.Honestly they look like they will be Really Nice Once they are Finished! Sorry I Dont mean anything bad just that you did such a good job and where so worried about the Cork on the BOTTOM but if you would like truthful feedback I think if you take just a bit more time you could come up with a easy way to Jazz up those coasters! Maybe some sanding swirls purposefully done in a patteren of your liking or maybe chuck them back up in the lathe and add a few detail groves, etc.....
Anyway thats just my opinion and its worth Exactly what you paid for it!