For the most part, a pound of meat sliced at standard thickness and spread out to once slice per sandwich will make about 21 total sandwiches. However, this really depends on preferred sandwich thickness and the type of meat used. The thicker the slice, the less sandwiches can be made.
A pound of meat can last a long time if used sparingly on each sandwich, or it can disappear quickly if meatier sandwiches are preferred. Typically, there are eight slices of lunch meat for every 6-ounce package, as stated in the nutritional breakdown of turkey breast on "Self." So, if there are 16 ounces in every pound of lunch meat and one slice of meat is used per sandwich, a pound of lunch meat will make almost 21 sandwiches.