The SBT I currently own has:
.742" bore
.703" choke
.039" constriction

Ser. # 223403

JSH

Was wiping down a few today from the safe and measured bores.
SN 238162 SC 34" bore .730 Choke.036
SN 225127 SC 34" bore .731 Choke .031(Extended Forcing Cones)
SN 232323 SC 32" bore .732 Choke .033
SN 206107 SC 32" bore .729 Choke .036
SN 190625 SA1 32"bore .742 Choke .044 (Upgrade by Delgrego and Runge)

I feel 238162,232323and 206107 have untouched bores.
225127 has original bore and choke but forcing cones have been extended.
190625 has been upgraded (1972) and most likely had bores polished.
Hope this helps Paul:corn:

Parker SB Trap bores and chokes
 

Thank you very much Paul. That is exactly the type of information I was hoping to receive. Sounds like you have a very nice collections of SBTs!

Happy Thanksgiving - Scott

SC 228811 .733 bore .042 choke

SBT Bore and Choke
 

SB 190xxx .739 with .042 choke...

Trap3

SB Trap Bore and Choke
 

Below is a summary in table format of bore and choke measurements provided by respondents. Worth noting there are some "overbore" guns with really tight chokes. Also, several have relatively more "open" full chokes. Not drawing any conclusions. Thanks to all the responses.

Serial No.Grade Length Bore Choke
191142 SC 32 0.737 0.030
SC 0.730 0.040
SC 0.730 0.040
223403 0.742 0.039
238162 SC 34 0.730 0.036
225127 SC 34 0.731 0.031
232323 SC 32 0.732 0.033
206107 SC 32 0.729 0.036
190625 SA1 32 0.742 0.044
228811 SC 32 0.733 0.042
190xxx SB 0.739 0.042