In the 1979 recoding, the ELX_ wagons that were not fitted with standard ridge ridge were coded VOBX. The wagons in this group included flat side ELX's and those flat side types rebuilt with corrugated sides.
There were about three ridge gear types. Only the ridge gear type as seen on VOCX wagons was 'standard'.
The VOBX class were reduced in numbers by rebuilding to VOCX with corrugated sides and conversions to other open wagon types.