The serial number on my 100 is 89452. It was made in June of 1964.
The attachment is a Viking Landscaping Roller Blade.
There are 2 different attachments for the Viking.
Slicer attachment:
Scarifier attachment:
The Viking and My 149 are in 2 different books written by Hank Will. From what I've been told this is a rare attachment. The Viking was design to fit on all different garden tractors.