2nd class blue Machin security stamp Business Sheet M16L with Security Backing Paper
The 2nd class business sheet was reprinted on 26/01/15 and appeared at the end of March.
A new printing 01/12/15 appeared in early January 2016. These sheets have the repeated text ROYAL MAIL on the backing paper beneath the stamps. A further reprint with year code M16L was made on 18/01/16.
SG U2961 (also used for earlier years).
For some stamp (sources) the 2015 printings will exist in both forms. It may be that all the business sheets will appear that way. It may be that stamps from some sources will appear with unprinted backing paper in 2016 (eg booklets or counter sheets) with the variant appearing later in the year.
But the duplication is likely only in one year for each stamp source unless Royal Mail decide some time in the future to revert back to the unprinted backing paper.
This is the reprinted business sheet has now been reprinted with M16L year code on security backing paper.