Sorry for the delay (forgetfulness) in replying to this point:
... i was wondering if they may have made letter canes for putting into weights for other reasons except for the date
My understanding, based on details from the book The Complete Guide to Perthshire Paperweights
is that letter canes were only used for three reasons ...
a) a "P" (or "PP") cane as an Id for Perthshire Paperweights
b) a code for the years (A-Z = 1969 - 1994)
c) for use by those allowed to add their own signature canes
In the case of c) known people using signature canes at Perthshire Paperweights were: Jack Allan (JA), John Deacons (JD), Peter McDougall (PMcD) and a collaboration between Peter McDougall & John Parsley (PMJP).