That is a well documented model. It's called the M48bo. The "bo" stands for "bez oznake" translating as "unmarked" or "without markings." These rifles were "sanitized" for export. Many for those numerous "liberation front" type organizations so common in the '70s. It was kind of silly considering the Yugos were the only ones making that type of rifle at the time.A new Yugo M48 with NO crest.
Interesting. Are you sure it is a M48.?
Do you have pictures of the receiver by chance?
The first "bo"s were rifles taken off the rack, scrubbed and refinished. Beginning in 1956 it became a dedicated production model. It was actually the most numerous model produced but due to the fact that so many were exported, many being crested by their receiving nations, that there are relatively few available. These may bring a minor premium over crested models if matching.
Others are suspected of being "parts guns" assembled from parts kits and stocked here. There is some good source material to support that. Branko Bogdanovic for one. Many of the Mitchell's Mausers are obviously cobbled together too.
One rifle I know of had a bolt with the firing pin hole too small to admit proper penetration of the firing pin. This bolt/rifle was obviously never proofed.