Original sentence: - 250 BTR-50PK and BTR-50PU and 500 OT-62 TOPAS
Edited sentence: - 500 BTR-50s ordered in 1964 from the Soviet Union and delivered between 1965 and 1966 (the vehicles were possibly previously in Soviet service).250 BTR-50PK and BTR-50PU and 500 OT-62 TOPAS