After a very long 7 months worth of searching I have finally found what I was looking for and can now give a thorough update on the 1965 Canadian 5 Cent nickel with different 5's!
I feel like this hunch of mine has finally paid off to say the least, through my research I have confirmed the 1965 Doubled Die Reverse by finding quite the few (to me fairly common now as I have found more than 2 full rolls).
There was speculations that the smaller 5 I was seeing was merely due to the Doubled Die, however I have found an example that I believe to be from an SMS Set, as the queen on the obverse has frosting with a mirror like field, but the kicker with this one is it is NOT a
DDR and the 5 is still Smaller than that of the normal circulation business strike for 1965.
Here is a photo of the 1965 Regular Business Strike.

Now the following photo is of the 1965 Regular Business Strike, but with the
DDR (lighting somewhat hides the notch in the 5 but it is there)

Now I will show a photo of the original 1965 SMS 5 Cent Small 5
DDR I showed when I started this post a few months ago. The Following coin is the one that was speculated to be smaller
only due to the Doubling.

This following photo is the 1965 5 Cent SMS Small 5 with No doubling at all on the reverse proves to me that the size was never due to the doubling.

Last but not least, if you cannot see the difference yet, here is the Regular Business Strike, side by side with the SMS Small 5.

So in total, my research has me convinced that there are not 1, not 2, not 3 or 4 but 5 different varieties for the 1965 Canadian 5 Cent Coin.
1965 5 Cent - Small Beads
1965 5 Cent - Large Beads
1965 5 Cent - Doubled Die Reverse (regular 5)
1965 5 Cent - SMS
DDR Small 5
1965 5 Cent - SMS Small 5
All photos included have been taken from 90 degrees from the same height with the light pointed from 90 degrees as well.
Edit: I should say there are 6 varieties, as the 1965 SMS from what I have seen are also regular 5's and only some having the small 5.
Finding and discovering modern Canadian doubled die varieties since 2018.
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Modern Canadian Doubled Die Varieties - First Edition
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https://www.mcddv.ca - (New Site, Second Edition, Registry & Services coming fall 2026)