In a 1950 catalog they list the 186 together with the old number 1361 and the whopping price of 15.00 a dozen. the 136 is listed at 16.50 a doz. those bales are expensive..

1948 catalog shows with the old 1361 number. So I'll guess they switched catalog numbers in tween 1949-1950. They did this a couple more times in the 80's because of thse darn computer things but tried to keep the catalog numbers the same.
from 1950-1969 no shackle had 4 pins (in the catalogs pictures)
In 1970 the 186 is shown with a bale and 3 pins at 5.50 each
So we have it narrowed down to 1950-1970 for the 186 without a bale/shackle. The last year I see the 186 with the shackle is 1983. I Dont think we can get it any closer. IN all cases the blade is called a pruning blade and is in the horticultural section of the catalog and pricelists.
Now comes some confusion...
The 136 ,163 and 186 all have different bolsters (pinched?) than this one pictured.
Look at the 175 next to the catalog picture of the 186. Ok Im gonna go look some more..
Hope that helps.