Ejector Seat Numbers

Hi all

could anyone help with the following seat part numbers and what aircraft they belong to.

27L/50101 Dated 4/1961

27L/50103 Dated 3/1961

27L/103 Dated 7/1957 (I think this is a Mk1)

AS2142 Instructors Sliding Seat (on the label it say A/C 666 date removed 7/1978)

Thanks for any help given.

Colin