[falcon123]

i should think it must have been it was produced after 1974,this is due to the fact that the nato stock number includes a "country code" which is 99. 99 is for u.k. up until '74 the nato stock number didnt have the origin country code as it followed the old f.s.n (federal stock number) system of the us govt. 00,01 are u.s. designators. as its quite likely it originally was an older design that remained in service over a period of years.later productions and replacement modules would reflect the stock numbering system of the era in which they were produced