Appears to be a M1842 musket. This would be a 69 caliber smoothbore. The existing lock plate is dated 1855, which would be in the latter end of the manufacturing of the M1842's. The lock plate has "Springfield" on it, however the hammer present appears to be a Harpers Ferry made type...
Unfortunately the weapon has been cut down... at least the stock has been.... or commonly referred to as "sporterized".... Many of these weapons were sold off rather cheaply post war... One of the common civilian uses was to cut it down in such fashion to convert it into a hunting shotgun... A lot of these like this out there. Interesting wall hanger for sure.... Unfortunately it also greatly hampers the historical or collector value.