[swarmee]

Originally Posted by 53toppscollector

That comes out to 172 total....so, there are close to 200 SweetCaps that were not labeled by series/factory. Which is a problem when trying to figure out actual pops.

Exactly correct. Early on, PSA just did T206, then added the backs. Then they did the Series (150/350/460). Even later, they added the Factory information.
Early flip (before half grades when Fair was broken apart), just T206:

1909-11 T206 - [Base] - Piedmont 350 Back #HOBA - Home Run Baker [PSA 1 PR]
Courtesy of COMC.com

Flip starting with 209 (maybe 10 years ago): Only "Piedmont"

1909-11 T206 - [Base] - Piedmont 150 Back #BOGA - Bob Ganley [PSA 1 PR]
Courtesy of COMC.com

Flip starting with 246 (maybe 5 years ago): Piedmont 150

1909-11 T206 - [Base] - Piedmont 150 Back #GIBS - George Gibson [PSA 3 VG]
Courtesy of COMC.com

Newest flip info:

1909-11 T206 - [Base] - Piedmont 350-460 Factory No. 25 Back #LADO.2 - Larry Doyle (Portrait) [PSA 3 VG]
Courtesy of COMC.com

Someone would have to pay for reholdering to have all the true flip information added, which doesn't really make much sense unless you're trying for a Master set registry or when you're planning to sell. There are many rare backs that are still only labeled "T206". And PSA still doesn't break out T205 backs, so those are completely blind when it comes to manufacturer.