Is that a TBird pickup in the middle position? Looks like a good idea.
lea.jpg
https://www.youtube.com/watch?v=9apFhvsIWRY
No, it's not a Thunderbird pickup. It has a black mount ring plus the typical John Birch row of pole pieces
Like this
(https://www.dieter-goelsdorf-history.de/uploads/images/Gallery/Englisch/Technics/Pickups/John-Birch-Pickup.jpg)
Yes exactly a John Birch pickup.
Interesting that Jim Lea wasn't a fan of John Birch's unauthorised modifications to this bass, yet it appears there were at least two phases of modifications? This looks like the original factory finish, pickguard etc but two new Birch pickups. The full white refinish came later, complete sure additional pickguard etc.
(https://www.laney.co.uk/blog/wp-content/uploads/2021/10/Jim-Lea-Laney-Get-The-Sound-Slade5.png)
Jim's EB3 very early on was fitted with the John Birch pickup and stayed in that configuration until I think 1974. At some point Jim had mentioned to JB that he might want his EB3 painted white. So when Jim's bass next went in for work it was painted white and received the white double pickguard, Jim was not pleased but he continued to use the bass until it was stolen from John Birch's shop along with a number of other instruments. Jim was then supplied with his all maple sunburst John Birch EB3 clone.
I assume Birch leant Jim basses while the EB-3 was going under the knife.
(https://i.pinimg.com/736x/52/ed/f1/52edf1a31c0719c0e5978612bbf8c44e.jpg)
(https://i.pinimg.com/736x/86/07/88/8607884a40ca0b978521c35d9abbe318.jpg)