I have two Pool rifles, an earlier fullstock by Stephen P. Pool, and a nicely inlaid halfstock by his son, Sanford P. Pool...and I would greatly enjoy seeing yours. I "gather" original lock plates and may have one that fits your rifle. Some of them are not complete locks, but I always prefer to use an original plate on an original gun when a lock is replaced...and if a complete lock of the correct size and geometry can't be found, I will have an original lock plate rebuilt, so the outside/surface is still "of the period."
There are three (3) Pool rifles that are well illustrated in vol. I of the recently released book, "Kentucky Gunmakers 1775-1900," plus useful biographical information on the family members that built guns in vol. 2 with 1,100+ biographies of early Kentucky gunsmiths. The 3 illustrated rifles include: an early gun by Stephen with fine iron work and some interesting carved details, a later flint gun by Stephen with his outstanding filed iron work, and a neat little halfstock by Sanford...almost the spitting image of the halfstock that I have, except that mine has a good deal of German silver inlay work. If you have any interest in the book, there is information on this site under the "To classified forums" section, under "New books." Hope you can post pictures of your rifle. Both father and son did excellent work, the elder did fine iron mountings. Shelby Gallien