T-Mar

To clarify any potential misunderstanding by forum members, the "S" in the serial number itself reprents the unidentifed manufacturer. They manufactured bicycles under contract for other companies, that were marketed as Nishiki, Sekai, Shogun and probably several others. We can now add Huffy to that list. The first numeral in the serial number (in this case "1") is the year code. The "F" appears to represent June. This is consistent with the format found on the OP's Shogun 400 (serial number S3L01485), so it would appear to have been manufactured by the same company. The "S(1)" designation is that used in my Asian Serial Number Guide to represent the first of the unidentified manufacturers having a serial number format with an "S" constant.

We've seen this same frame marketed under other brand names, so it's likely a standard offering from the manufacturer, that they then painted, branded and equipped to suit the client. I imagine that orders for folding bicycles were rather small, which does not make for efficient production and a decent profit margin. Consequently, I suspect that the manufacturer built these to speculation. The frames would be stored, then painted, branded and equipped as new orders were received. This could explain the frame pre-dating the front hub by the realtively large period of five months. Another possibility would be a defective frame that had to go through a rework cycle.