This excerpt from the PSS Town & Type catalogue shows how difficult it can be to figure out Chicago precancels without having your own catalogue. You need to have the catalogue handy so you can use it as a template to measure the exact spacing between the lines, the spacing between the town name and the line, the small details like where the second "L" lines up under the "H", etc.
In addition to the line shown here, there are many other types which have a similar appearance.
Ryan
