Hi John,
I agree with Mike at first glance. The sideplate, lock, and other hardware look Dutch from the late 17th or very early 18th century. The stock shape is also early, perhaps 1680s-1690s period styling. It would help sometimes if you have other information about the provenance of the guns you post because often styles transcended places and time. For example, the styling of British military muskets from the late 17th and very early 18th centuries was often determined by the regimental colonel not government ordnance. In that system, cheap arms and designs were often obtained from foreign countries with Holland being a prime supplier likely owing to connections of King William to his native country.
dave
