well on that
serial number you cant.....that means it was made before 1987.....so you really dont know the time of prodiction, Hoover ONLY sarted doing that after 1987....and rember???....it has to make SENCE.....the first two number would be the month ( 01 - 012) and the last two are the year....so 0018...dosent make any sence for a Hoover convertible.....so it was made before the time of the dates being written in the serial number......does that help a bit more?
some of the later Convertibles were somtimes made right when this was started, so some would be made bfore 1987 when this method of dating was not yet used...then 20 or even 100 more machine off the line later could have been then dated since hoover models seemed to run for atleast 3 years...