Actually, we have seen a Nishiki track frame before. However, we weren't able to come up with anything definitive. We've never come across a catalogued track model but I don't have a complete set of Nishiki literature and we also know of uncatalogued road models. So, there's the possibility of an uncatalogued model, a foreign market model or a custom built frame for a Nishiki sponsored rider. Regardless, the serial number formats don't match any of the known Kawamura formats, so they appear to have been contract built. What is interesting is that the formats are very similar with the other track frame being 73 0042. I'm wondering if one or the other is confusing a T as a 7 or vice versa? Pictures of your bicycle may aid in the detective work, so please post some. Unfortunately, we can't compare it to the other Nishiki track bicycle that has surfaced, as the pictures have been deleted. The other track frame appeared to have been from at least the 1980s based on the embossing and it had a bottom bracket dating to 1989, but that could have been a replacement.