Originally Posted by T-Mar

xmoksax, welcome to the forums. I'm not familiar with the Amust brand but Shimano Exage 300LX was a short lived group that would place it 1991-1992. The serial number may represent December 1990, which would be consistent with a 1991 model. Your paint scheme, with a fade from blue to yellow, was also popular during this period.

Nishiki was not a bicycle manufacturer but a bicycle brand. The rights to the brand were held by various companies and could vary from country to country. "Produced by Nishiki" is ambiguous and could be interpreted several ways. It could mean that the brand was owned by the same company that owned Nishiki. It could also mean that the owner of the Amust brand contracted the owners of the Nishiki brand to have the bicycle manufactured via one of their suppliers. Marketing people tend to push the boundary on labels like these, in an attempt to sell more bicycles. Putting a recognizable brand name like Nishiki on a minor or new brand would help to stimulate sales.

Certainly, the serial number format is consistent with that of one of the known contract manufacturers of the Nishiki brand during this era, so there is a connection, though I can't define the exact nature of the connection. In late 1988, Derby bought West Coast Cycle, the company that owned the rights to the Nishiki brand in the USA. I don't know how many non-USA rights Derby had acquired by the 1991 model year. Can I ask the country of your location? It might provide a clue to the nature of the "Nishiki" connection.