How did you permanently mark USCG NO.

if you dont' have a router handy, you can use adhesive numbers and cover them with a layer of glass and resin... i usually put that in the anchor locker at the bow since wall space in most ER is usually too valuable!

Although it's supposed to be permanently affixed, I've seen it many times (and shown same to boarding officers) in stick-on #s. I think most people understand that there is no such thing as permanently affixed, although RER has it right. I usually find them (and recommend that people put them) visable when you open the engine hatch. The CG will be looking in there anyway. The alley side of the engine bed is usually a good spot.

You could pick up a stencil at a craft shop, pencil it in and then Dremel that out or even paint it. I wouldn't recommend Dremeling stick-on letters as they'll tear off part way into your job. I've seen people simply use those stick-on letters and they got no complaints even though that's obviously not to code. With a commercial or certified vessel and maybe large private yachts they're sticklers, but for most recreational boats they're more concerned with how many PFDs you have when they inspect.

You’re making this way too complicated. Clean the area with acetone. Put on the self stick numbers, put a coat of resin/hardener over it and call it good

+1

If this is on a sailboat and Bristol is what you're looking for make sure you find a nice piece of wood. Where you're at some nice redwood might be nice (or is that like oak here). My experience with sail boaters is they tend to fall into two groups, either messy or pristine with an eye for the details. Sounds like you're in the 2nd group.

If you want something harder to remove or wear off, try using an engraver or etching tool and put it on something metal.

And how do you permanently affixed that to a fiberglass boat??? Decals and a coat of resin is the only permanent way to affix the official registration to the boat.

but I guess the poster can continue to operate his vessel illegally!

A marine Sign Shop in San Diego uses a local carpenter to make a wood plaque that has the numbers cut in with a router using templates. The numbers are 1/4" deep, painted black inside, and the plaque is attached to the stringer. I'm sure the method varies. but tabbing it on with glass cloth and resin would leave the most blemish if the thing was chipped off.
The whole concept is rather absurd, because there is no defined location for the Doc numbers where it can easily be seen if they were destructively removed, or, in the case of clearcoated dingy numbers; simply painted over. Every time an inspection team has come aboard, I've had to direct them to the location of the "indelible" Doc number.
Even HIN numbers are in a variety of places. Some vessels hide them in compartments, and, a hull extension really confounds it.

I had a stencil made and spray painted on the side of the engine bed /stringer. I guess one could glass over to make more "permanent".

So this is not the Hull ID?