Sorry, I wasn't sure of the intent of your statement, but because many people claim it's ok to use businesses that are not FFLs for engraving, such as "trophy shops," I think it's important to clarify that point.
Also, I'll clarify my own post. Some business that aren't primarily gun related, including some trophy shops, do get an FFL so they can include things like engraving firearms in their business. I used to do business with a trophy shop that had an FFL, for that purpose. They did lots of firearms engraving, both decorative and for NFA Form 1 purposes. However, that seems to be the exception in my experience.
Also, there is no exception in the law that allows gunsmithing, including engraving, without a license, if the customer waits at the business while the work is being done. That is a myth I often see/hear repeated. There is an exception to the record keeping requirements of an FFL, that they are not required to enter the firearm in their A&D record if the firearm is returned to the customer the same business day, but the business must still be licensed.
https://www.atf.gov/firearms/qa/does...cquisition-and