Mongrel maybe. A bunch of stuff that doesn't really fit together: Slab board neck with plug on headstock, F neck plate with no serial number (plate looks brand new), transition logo but font for "Telecaster" doesn't look quite right, 5 hole pickguard and barrel style switch tip but plain steel saddles, looks like there's a logo on the pickup, etc. Anyway it looks like a mix of features from the 50's and 60's, but not consistent. Have you tried taking the neck off seeing if there is any info on the end of the neck or in the neck pocket?
No serial number on the headstock or any of the hardware.
Pretty sure it is a partscaster, just didn't know if there was a way to tell for sure if it was a production model that may have been modified.
The bridge pickup is a Seymour Duncan, obviously not original. I picked it up because it plays and sounds great. I might end up selling it at some point, and I just didn't know for sure if it was a total mongrel, or just heavily modified.