1966 Dollar Large O Small Beads?

Large bead.

I have been trying to figure out how to tell the small from large and I'm still confused. I found 3 1966's in my coins. Is there one specific area to look at?

Easiest way to tell is if there is a business strike reverse and a fully prooflike ,somewhat baggy obverse that looks like a 1965 prooflike dollar , accompanied by a rather large purchase invoice from one of the prominent coin dealers of the 1960s.
These small beads dollars are mint back door jobs of somewhat dubious character. They were NEVER available through regular commerce. The best description is that of " Contrived Mule".
These can usually be found in a collection with a Double flip strike Goose Dollar and a Diving Goose on the same invoice.
Sarcasm fully intended.

Have actually owned two of these pieces . One walked in to my shop about 1989 . Originally purchased from Benny Lee Ltd of Vancouver BC . The second piece came out of a collection I purchased at a US coin show in Chicago early 1991. The original source of that piece was Silver Dollars Registered in Ontario.
The coins are accepted in the market place but are not considered to be a part of a regular dollar collection.
Unofficially , around a half bag (485 pieces) miraculously were somehow released from the HULL branch mint which was responsible for collectors coins at the time.