Hi Albert,
Lock panels are critical features that if done poorly, severely compromise the appeal of a gun regardless of how well other features are done. The challenge is to merge the rounded forearm and wrist with the flat sides of the lock area. Some makers carry the curves through the lock area very well and the panels almost look like they were glued to a round handle. That is easier to accomplish if the panel molding around the lock is very narrow (1/16"-1/8"). Other makers have wider panels and create a boxier look but often that is still very attractive if done well. For example, look at many of the better made 19th century southern guns. There are no hard and fast rules except that I would say any panels with >3/16" of flat surface showing above or below the lock will be hard to make look appealing. Generally, late 17th century and early 18th century flintlock guns had very narrow moldings around the lockplate. In some cases, there was no flat surface at all. That was the popular fashion and I think it nicely graced the round-faced locks often used at the time. There are always exceptions. I saw a beautiful pair of Piraube pistols made in 1690 with flat lockplates and wider moldings. Nonetheless, narrow panels were the norm. That seemed to change in the late 18th century and into the 19th. Wider panels, but still attractive, became the norm, along with almost universal use of flat lockplates. You can really see the changes in fashion by looking at British dueling and coach pistols through the 18th century.
dave
