What is the difference between TM/SM and the R in a circle (®) on certain marks?
The trademark symbols TM (trademark) or SM (service mark) gives the public notice of your claim to a particular mark, regardless of whether you have filed an application for federal registration. Use of the TM/SM designation, however, does not provide any legally enforceable right or additional protections under the law than if you did nothing at all. The federal registration symbol, the R in a circle (®), is for use only on trademarks registered with the U.S. Patent and Trademark Office (USPTO), not for pending applications. Furthermore, the registration symbol may only be used on or in connection with the goods or services specified in the federal trademark registration.
