As mentioned, it's probably a Lippert. Why don't you call their customer service dept. with your info and perhaps they can help you. They have a wide selection of replacement pin boxes too. Their number is 574.537.8900.
Called Cedar Creek and they gave me a number to call for a regional parts manager. I gave him my vin number and he confirmed it was a Lippert 1621. He returned my call and was so very nice. Of all the discussions on this forum, no one mentioned their pin box number. It would help others doing research.