Original model 1924 rifles as manufactured by Yugoslavia had straight bolts. There was a very limited exception. Some M1924s were configured as "carbines" by adding extra sling swivels as on the vz24. Some few of these were given bent bolts. These bolts are very rare costing as much or more than a rifle IF you could find one for sale. They differ from the M48 bent bolt in having a serpentine shape bolt arm and a checkered flat.
Here's a link to a photo comparison... http://www.milsurpshooter.net/topic/10243
The M48 was only made with bent bolts, no exceptions.
The M1924, 24/47= a refurbished M1924 and M48 are the same actions and the bolts interchange (allowing for headspace)
It sounds like your M48 got an M1924 (24/47) bolt.
Conversely, Samco's bent bolt 24/47s have M48 bolts.
Here's a link to a photo comparison... http://www.milsurpshooter.net/topic/10243
The M48 was only made with bent bolts, no exceptions.
The M1924, 24/47= a refurbished M1924 and M48 are the same actions and the bolts interchange (allowing for headspace)
It sounds like your M48 got an M1924 (24/47) bolt.
Conversely, Samco's bent bolt 24/47s have M48 bolts.