Is there AM? I’ve never heard of it, usually it’s just TM or R (R plus a circle).

"TM" is commonly seen in foreign trademarks. It is the abbreviation of the English "trade mark", which means "trademark". When the trademark has not become a registered trademark, marking the "TM" mark is to tell consumers This graphic or text is used as a "trademark" for goods or services, not a name or an advertisement; and "R" is the abbreviation of "register" in English, which means "registration", and what it marks is a registered trademark. It is protected by national laws and cannot be used by any other individual or organization without authorization. The degree of legal protection they receive is different.