One solution might be to use your readings in square brackets, and refer your readers to an authoritative list which gives meanings for most of the abbreviations of letters one is likely to come across when deciphering old documents.
Such a list is contained in the preface to "The Record Interpreter" compiled by Charles Trice Martin, the second edition of which was published in 1910. A facsimile of this book was published by Kohler & Coombes of Dorking, SURREY, England in 1976. I don't know if this is still in print (probably not!), but is likely to available in academic or large city libraries.
One problem with this, however, is that some of the original symbols had several different possible meanings. A common example is lower case p with a stroke across its descender. This usually means per, but can also mean par or por.
Just a suggestion, for what its worth. APOLOGY - Have just realised that Dorking is in Surrey, not West Sussex
Roger