Between January 1884 and December 1909 a sequential numbering system was used to register designs.
No actual date of manufacture can be inferred from a RD.
.........however only "OLDER" bottles carry these.
These numbers are far more prevalent on crockery than bottles.
RD. 1 - 19754 1885
RD. 19755 - 142300 1890
RD. 142301 - 248200 1895
RD. 248201 - 351202 1900
RD. 351203 - 385180 1902
RD. 385181 - 424400 1904
RD. 424401 - 471860 1906
RD. 471861 - 518640 1908
RD. 518641 - 534970 1909