The bottom line is that I don't know. There was an actual Royce Union bicycle company, so it wouldn't appear that Royce Union was just a private label brand sold only through the owner's retail chain (like Sears with Free Spirit). This would indicate that the brand was probably available to any retailer, though it's possible that there may have been protected territories, so that only one retailer in a region could sell the brand.

Royce Union also owned the Savoy & Sutton brands. Again, I'm not sure if these were in wide, open distribution. They may have been used to supply retailers in regions where there already was a Royce Union dealer. This was a fairly common tactic to expand coverage in a region, without violating contracts.

If a chain store signed a contract for any of the brands, there could have been quite a large protected territory that would have resulted in the brand being associated with a particular chain. I also wouldn't rule out the possibility of Royce Union having acquired these brands from a chain (brand history can get quite messy with acquisitions and divestitures) or that they were used specifically to service a particular retail chain who did not want the cost and maintenance associated with owning the brand. Sorry, I can't provide a definitive answer.