In addition to the 3 volume Identifier and the Lyons Pricing Guide, check out the website for the Carriers and Locals Society. Under References, you can find a growing group of various forgeries and fantasy issues organized by name of post. Also, on the PDF Downloads page, you can do a full Google-based word search on all the issues of the Penny Post (except the most recent 5 years are for members only.)
The URL is
www.pennypost.org***Typically posting links is disallowed until person has 50+ posts, but an exception being made here - Mod***