Ian,
The two models that you mentioned are indeed different from a regulatory perspective. Occasionally, a major regulatory agency such as the FCC or ETSI changes regulations during the life time of a product forcing the manufacturers to retest a previously certified product with the new rules / regulations. Normally products are grandfathered in for a 18 - 24 months but after that you either take the product off the market or you retest the product using the new rules. As a manufacturer you have two options: 1) create a new product SKU (very disruptive to sales, services, customers), 2) keep the current model but identify internally via the software so as to enforce any new rules or regulations or 3) prematurely end-of-sale the product. We opted for #2, retesting the AP3825i using the new DFS / FCC regulations and keeping the same model number to reduce disrupting our customer base. We introduced a new hardware identifier via a new hardware rev number, hence the different internal models numbers. Internally in the software, there are different regulatory tables and parameters for the AP3825i and -1 derivative.
Thank you,
Will