What’s in BT364?
The National Archives guide describes this as a Combined Index with extracted CR1, CR2 and CR10 cards which have been taken from BT348, BT349 and BT350. It states that the reasons for doing this are unknown.
The following is my understanding of BT364 based on my research of a small sample.
I suspect that at the time of the 1941 Bevin reorganisation all the active seamen index cards were removed from BT348, BT349 and BT350 and placed in a new active file. I suspect that the cards were arranged alphabetically by surname and an individual could hold several cards.
As time passed active seamen and new entrants were issued with new or replacement discharge books and the resulting CR1 card was added to the active file. Then, periodic reviews were introduced. I suspect that active seamen continued in the active file which became BT372 while the records of men who were judged to have left the sea were placed in BT364. I have found that the most common post 1941 records in BT364 are CR1 cards. BT364 cards are arranged by discharge number which makes them difficult to access.
Example of cards found for one individual
John Fagan, born Rush, Dublin 1896. Discharge A Number 760627
Original CR1 card from c 1914
Renewal CR10 card from 1921 with photo, (Cancelled CR10 card is in BT350)
CR2 card with 30 voyages noted from 1922 to 1941
CR1 card from 1931. ‘Discharge book reported lost’
CR1 card from 1948. ‘Original discharge book full’
CR1 card from 1953. With photo
After 1948 , cards have the National Insurance Number added
The record cards cover nearly forty years at sea.
I would expect to find the record of his post 1941 voyages on his CRS10 card which ought to be in BT382.