Hello, Jim
I realize you're not looking for indefinable Thomas quirks, but unfortunately they are there within the individuality of each rod finisher who dressed the grip and reel seat. We don't know exactly who finished any particular rod, although Billy Edwards worked part-time in that capacity for two decades. The lathe was a simple Fay & Scott model, made in Oxford, Maine, not a refined piece of machinery by modern rod-making standards. Take a look at it:
Thomas used full metal seats purchased in "the raw" from Montague, originally developed and produced by George Varney in Central Valley, then in Poughkeepsie, finally moving his machine to Montague City. These "reel plates" were used by every Leonard-school maker. Thomas modified three styles, the dimpled version, a railed version, and a plain version (the most common). Here is a photo of the three styles:
I would think that you would find variations-- "quirks" as you call 'em-- in the lengths and positions of the rails, perhaps even the pocket, depending
who was finishing them. The human animal is an imperfect organism.
As far as I can tell, the same quirks would be found in the Thomas cap and ring seat. Yet by design alone, the seat is consistent. In the photo below, we see an early version (no number), and below it is a later version (#30 on the butt cap). They are remarkably similar in detail, right down to the trim rings. Yet handwork had variables, and I don't think we can superimpose modern technological
facts back to a craftsman working at a Fay & Scott lathe. In this light, the minute variations you perceive as worthy of a special number probably didn't exist in the handcrafting days of Fred Thomas.
However, if you wish, I can measure the length of the various Thomas reel seats I have in hand and post them. Like I say, I doubt the difference of 1/4 inch was significant to Fred Thomas.