How to adjust the speed dial of a18 size lever set thanks
If you have one of the more common style pocket watches like Elgin, Waltham, Illinois, etc., the adjustment of the spring tension on the balance wheel spring or "hairspring" is virtually the same for most models. It doesn't matter if the watch is a Crown (stem) set or lever-set. Open the back cover, and most watches will have a second dust cover protecting the movement.
On the main housing cover of the balance wheel and hairspring configuration is a small adjustment lever. Note the current position of the lever now, and move it slightly (very, very slightly) in the direction you need to correct for. Most movements will have "S" for Slow, and a "F" for Fast. Of course this is pretty obvious for most people. This adjustment will cause the balance wheel hairspring to become a little shorter or tighter for the faster adjustment, and therefore, cause the watch to speed up slightly. The reverse procedure will "lengthen" the spring, and slow the movement down.
Since you're apparently doing this yourself or for an associate, be careful with these adjustment, making certain to not slip and damage the wheel or spring. Run the watch for several hours, and compare the timing accuracy with your known amount of error, then make further adjusts if needed.
Of course, you still may wish to take it to a certified watchmaker or repairman for this service, especially if the watch is a heirloom or otherwise valuable piece.
Good luck with this procedure! Let me know if I can be of further service.