It's definitely entry level and that is a typical Japanese serial number format. It can be reverse engineered a few ways, with the most likely years being 1972 and 1973. A sanity check indicates it is in ballpark, as it still has down tube shifters and there do not appear to be any brake safety levers. However, I am a bit surprised to see a chainring guard.

Unfortunately I can't name the manufacturer. What I can say is that the format does not match the few know Zebrakenko serial numbers. However, that does not conclusively prove that there are no ties, as there are various Zebrakenko formats, indicating that they were probably contracted.

Is that a stylized Zebra head in the upper right hand corner of the badge? Picture please! TIA,