(https://imgur.com/gallery/1-0-senator-assembly-numbers-9q9glcW)
I was taking apart a 1/0 Senator i got on eBay and noticed the number 2 on spool and both side plates. I haven't seen numbers inside my other senators. Did Penn use assembly numbers or maybe the previous owner marked it for some reason?
https://imgur.com/gallery/9q9glcW#4PX3WPO
Yeah, I've never noticed that on any of mine. So I'm not help.
You should draw a weiner on some of the internals just to get a chuckle out of a future owner many years from now.
Looks hand-made. Had a 1/0, sold to someone here. It was unused in the box, no marks like that.
I had an International 975CS that I serviced for the original owner, and he was pretty confident it had never been serviced. It had a number scribed onto the inside of the side plate (I think it was a 7, but not sure). - john
They are called "makers marks". It was a pretty common thing to do a century ago when manufacturing was not so precise and the parts didn't always fit together just right. I've never heard of a modern example.
Does the reel otherwise have normal part numbers? Wondering if this was an early example, perhaps a prototype