Hi Geoff
Interesting one this !
I recall when my Dad bought Seal 22 * 7 which at the time was about 3 years old, he made contact with a few other seal 22 owners time and one such problem arose,
He contacted John Baker with this question and was told that hull were being manufactured in quick succession over a short period and once sold sails were placed on the boat but not necessarily with the same matching hull /sail number
My 22 "Snafu too" had hull number 176 and 271 on the spinnaker and 271 on an original old main but nothing on a the newer one when i bought her
I suspect there is a lot of 22 with this .
(I kept it as 271 as it was a later number !