The IGI has a listing "United Kingdom Merchant Navy Seamen Records, 1835 - 1941"
The period I am looking at is 1845 - 1854 and although there is no Image available there, the film numbers etc are noted, so perhaps when I visit my local FamilySearch Centre nearby, the image will be there.
The 'Event Type' on the listing is "Military Service".
What did this actually mean, during the 1840's? some kind of reserve-list? additional training?
Any light on the subject appreciated.