Actually, Cromwell does have a national service mark for "Party" and filed a suit against a station in Toledo, OH over this in 2022 that was resolved in 2023. Apparently, the service mark was renewed in 2019 for another 10 year period, although the article cited calls it a 'trademark'.
From Inside Radio:
The Cromwell Group has dismissed its trademark infringement lawsuit against Fusion Radio over the use of the “Party 103.3” moniker after the two parties reached an out of court settlement.
www.insideradio.com