Four SK4s were built to “stage 2” and delivered one per month in Jan/Feb/Mar/Apr 1977. XZ870, 871, 872 and 873. This was probably under a Development contract as the production contract for the first batch of 10 was let in 1978.
These four cabs were then completed and redesignated ZA290, 291, 292 and 293; delivered in Sept 79, Nov 79, Dec 79 and Jan 80 respectively. The first SK4 flight was on 26.9.79 (ZA290).
Four more were delivered between Apr 80 and July 80. The aircraft in question, ZA298, was the 9th SK4, first flew on 21.8.81 and was delivered to MoD on 1.10.81. As the pilot offers a slightly later date this was probably a “paper” hand over.
However, Westland’s records show ZA298 to be “ex demo G-BJNM” implying she was hawked around the bazaars for a while. Nevertheless, she looks to be a long way from being the oldest, albeit part of the original production run.