Small update. I just found the following info on page 35 of the Marlin 2012 online PDF catalog.
"INVECTOR CHOKE SYSTEM
* Fits most H&R shotguns with screw-in chokes. The exception is the Excell Shotguns
*Available in 12 and 20 gauge. - Modified, Improved Cylinder, Skeet, Full, Extra Full, and Turkey
* Can be used for Winchester and Mossberg Firearms as well"
Which , of course, suggests that the H&R's, Winchester's, & Mossberg's all share the same type of chokes.http://www.digitaleditiononline.com/pub ... 9652&pre=1