The 'dried waremarks' that you had were probably etch marks caused by acid. I know you'll say "we don't use acid on the counter", but even mild acids like those in alcohol, red wine and vinegar will etch marble, especially darker colour and even more so on orange/red coloured marble. I don't think that urethane is the answer, so to remove that you will probably need to have the marble re-ground and then polished. There should be people in the yellow-pages that can do this with only a moderate disruption in your house. If you choose this route after all is done apply several coats of top quality natural stone/marble sealer-and exercise caution with what you leave on the counter. Hope this helps.