Thanks for the photo. I can’t see anything wrong with your SN. All characters are consistent with factory stamping for a 54 Pan and here are two examples for comparison. This first boss doesn’t appear to have flaws under the characters but the second has them similar to yours. Also notice the second 5 appears to have what may be a defect or abnormality and it seems to have become more noticeable as the years went by. Your 5 may have the same thing?
Eric

 

Thanks for confirming that for me! Hard to tell if its an abnormality of the stamp or how the person struck it, like the F in one of your examples.

 

Here's a better example of the unusual 5.







Next SN has a different 5 in the year portion which was probably done with a tandem stamp. But the sequence 5 appears to have the defect.
Eric

 

Defect in the 5 maybe?

 

Yours looks slightly different in close-up? But these Servi-Car 5s appear to have it.
Eric

 

Thanks again Eric!

Took it for a ride yesterday, a few observations. I love it! But it would benefit from having a front brake and its not a bike I would be inclined to ride fast even with better brakes.

Need to sort out some electrical because there's no regulator and the cutoff relay isn't connected but its there on the engine case. Should put a horn on it too, headlight doesn't work and I'll relocate the license plate to the back of the sissybar to get rid of the side mounted setup. Could use a rear tire


.

 

We would go to Coney Island after the gin mill at 3 am for Nathan’s hot dogs at 70mph over the Verrazano bridge then down the belt parkway

*****

you think a brake is going to save you with that type fork - lets just say its been tried before

 

A wise old-timer once told me he had a close call on a bike with no front brake and vowed to never do that again......oh wait it was you!

 

It's funny how people back "back then..". It was what you knew and didn't know any better. Now you do! Lolol