According to Fire & sea/Smoke & Ice (same data in both) a five digit code was in use from "the early 1970s" and up until 2002. The first digit (4) indicates a vase, the second and third digits indicate the year (86) so possibly 1986 but I would seek confirmation of this. No mention of the last two digits, possibly designer?
The various signatures and numbering systems used by Boda, Kosta and Afors before and after they merged can sometimes be a bit tricky to decipher. In other words you need an expert.....
John