Mysterious Tricone...

[Logan Day]

Aloha everyone,
I just a purchased a vintage National Tricone at an estate sale which I am head over heels for. However, there's no serial number visible on the guitar. It looks to me like there may have been one on the top of the headstock which has been filled in. Someone also scratched some strange numbers into the neck :"117L 174X501"

Does anyone have any clues as to the age of the guitar? The numbers? Thoughts on the guitar itself? All I can gather is that it's probably after the first 2400 made as they were all stamped on the back of the neck

Thanks everyone

[Logan Day]

More photos:

[Ben Elder]

Early-ish ones were stamped on the back of the neck. Did you check near the strap button? (Kind of a roundneck thing.)

[Noah Miller]

Pictures of the front may be helpful in dating.

[Logan Day]

I was having some trouble with the image size limit, got one up there now

[Logan Day]

Early-ish ones were stamped on the back of the neck. Did you check near the strap button? (Kind of a roundneck thing.)

I did, there's no serial number anywhere on the outside

[Eric Dahlhoff]

I have an early tricone that has the serial number also written in pencil on the inside. (and as usual, stamped on the neck)
So you might try taking off the cover plate and looking in there.
And of course, vacuum out all the dust!