The George Lawrence Company produced equipment from leather saddles to riding gear, chaps and gun holsters. The company was in business from 1876 until it closed in the 1980s. Each Lawrence holster had two numbers stamped into the back. The first number designated the model of the holster, and the second set of numbers gave the size code. With the George Lawrence Company out of business, there is no one place to find a complete size coding chart. To find the size for a Lawrence holder, there are sites online that can help you determine what guns fit in the holster.
Use an online site like Vintage Gun Leather to determine what guns go into the holster that you own. The Vintage Gun Leather site showcases many models from the George Lawrence Company for both automatic and revolver holsters. Compare what they have with your model. If they have your model, the description of the holster will tell you what gun will fit into that particular holster.
Find old catalogs that had the George Lawrence sizing charts. George Lawrence had their own catalogs, and Stoeger Arm Company's and Herter's catalogs carried the sizing charts for these holsters. These catalogs can be found on websites such as eBay and Amazon for sale or auction. They may also be sold on collectors' sites such as Cabin Creek CDs or Vintage Gun Leather. You may be able to purchase the catalog on a CD and store it on your computer.
Go to local gun shops in your area. These stores, if they specialize in antique firearms, may also keep a sizing chart for the George Lawrence Company. Gun shows are another popular attraction where you may find people who are very knowledgeable about the holster you own and what gun fits the model. You may also run across one of the old catalogs with the sizing chart included, depending on the size and scope of the gun show.
There are many gun forums that specialize in antique arms and equipment. These sites may be able to tell you just by the numbers you provided what weapons will fit your particular holster. Many forums are very supportive and if asked may provide you with a copy from a catalog showing sizing guides for the Lawrence Company. As with any forum, independently verify the information they provide before placing a gun inside.