I agree 100% with Scott here. Most likely, nobody is ever going to take the time to entirely update any or all of these old lists. However, he's correct in that they (in general) are full of errors. I can't speak to this Lancaster list with the authority with which that Scott or others may, but I can tell you that relative to old "lists" and books including information relative to Northampton county, I have found a ridiculous amount of errors and unverified information. However, finding the errors is generally a piecemeal task that only occurs when researching, say, one or two particular gunsmiths and then realizing that what has been previously published is just plain wrong.
Many authors up through the 1960s and 1970s were relying almost solely on earlier 20th century research, and much of that was based simply upon the old 19th century popular county history books; they themselves are full of unverifiable information. There are unfortunately authors even as recently as the last 20 years that are still engaging in the act of lazy regurgitation without question.
Question everything!