Unlike other monikers, "poorboy" is not a school or a region or a pattern so it is simpler to define.
On SM and TN rifles the "poorboy" name is generally given to guns which lack one, some or all of the following: buttplate, sideplate or washers, entry thimble, and patchbox. Sometimes they had a less elaborate trigger guard and only one ramrod thimble.
None of these items is considered "decoration"...each is a functional part of the firearm although not neccessary to make the gun fire.
This region was an anomoly in the time line of the longrifle and has little to do with the evolution of it. There were guns being made the same way here into the 20th century. Even today some areas are kind of a time capsule.
On iron mounted SM/TN guns each piece of hardware, often the barrel and sometimes the lock, was fashioned by hand or forged. By deleting items cost was kept down.
Many of the people of the region these guns came from were and still are poor but practicle and willing to forego decoration and extras on their guns as they did in everyday life.
The functional quality of a "poorboy" was generally the same but made more affordable by deleting these "extras".
The rifle we have here is not a "poorboy".
Enjoy, J.D.