The serial number for RM1 garden flower definitive now is 2011/2.
The RM1 stamp from this serial number (2011/2) is different from those of the previous two serial numbers (2010/1 and 2011/1). The difference is on the border of the stamp. The stamps from 2010/1 and 2011/1 have white border but the stamp from 2011/2 is without white border. So, the stamp from 2011/2 is a "new" stamp!