According to the Archives of Breitling, the present watch was made in 1973, fitted with a Valjoux 236 movement.
During a short period between the mid-1960s and mid-1970s, Breitling supplied a small number of single button chronograph watches to the Canadian Air Force, adapted following the specifications requested by the Ministry of Defence. The watches featured an unsigned white dial, a Valjoux 236 movement with hack feature, the outside of the case backs were marked with Ministry of Defence issue numbers.
The outside of the case back of the present watch is engraved with the following markings:
D.N.D. (Department of National Defence)
S/N NS 162
Stock No. 6645/21/802/1267
NATO stock code, 6645-21-802-1267, NATO individual device number for this type of chronograph, 21 is the country code for Canada within NATO.