Found it !!
According to C.Houston Price,(10th Edition), in 1972 KLAAS began to stamp Roman numerals (after the pattern number) beginning with XI for that year and advancing each year. Example 1975 would be XIV, etc. Guess those before 1972 can't be dated? J.O'.
$55.00 
$60.00 
$37.97 
$134.00 
$295.00 
$135.00 
$335.00 
$155.00 
$210.00 
$85.00 
$110.00 
$125.00 
$300.00 
$45.00 
$14.97 
$11.00