As for the revwar arsenals / shops it seems like there is a lack of correspondence regarding these facilities compared to other maker/contract correspondence. Was that intentional to keep these locations as secret as possible? Or have the records just not turned up yet? Like Allentown’s, the one at Lancaster seems mysterious.
I don't think there's a "lack" of material regarding the Allentown facility compared to other facilities? There is lots of material regarding the Allentown facility, including regular returns that indicate precisely how many arms were sent there and how many (repaired) were disbursed from there; we know lots about who operated it, when it was built, and when it was disbanded.
So if we're comparing maker/contractor correspondence with the Allentown facility, say: we have comparable info, if not more. We know information about who operated the facility, what they were paid, what their work involved. What we don't know, as Eric said, are
the names of the men who worked there (who worked under the heads of the factory).
It's worth thinking about how where such information would have been kept. Returns of incoming and outgoing arms survive because they were
sent to central authorities in Philadelphia. But payments to local workers (if they were local: these workers may have been relocated from Philadelphia, as the factory itself was)?: receipts would probably have been produced and saved, if they were saved, by the local managers. So what happened to Ebenezer Cowell's and John Tyler's personal papers? Who knows. Very, very, very few batches of personal papers by such "minor" figures survive today.
I suspect it would be impossible to recover a list of workers in almost any factory setting in early America, unless--miraculously--the materials from the shop happen to survive and those materials involve payments to workers (instead of just ledgers of customers or daybooks of daily work). Very, very, very few merchant's ledgers or craftsmen's ledgers survive. The ones that do enable us, sometimes, to reconstruct a whole world of workers, suppliers, customers, etc. But without such materials: total mystery.