I am sure he figured he would get a quicker answer on this forum. So far not so much help from me or others. So I took a stab at it. History of Case units shows that they have breakdowns of the model 1818 but show it from late 1986 - 1996 and I found on place that said what I explained above the whole digit number is both letters and numers when counting to 10 as the year. If that doesn't help then yes call the IHC/Case folks.
I understand asking here, as some times we all like to avoid dealers, and just being active on the site !
but when posting on a forum, your at the mercy of someone to reply and then hoping there correct(which could lead to getting wrong parts if they changed things between yrs)
SO, IMO< when a simple call to a dealer will net the exact info, and be had as soon as you place the call and get an answer on other end that is again correct
seems like a simpler things to do than hoping to get an answer on a forum, no offense meant and not trying to argue, just saying it maybe the better way to get this info and faster as well!