Hair Trigger
US Veteran
I checked GB and they didn't have any 66-1's for comparison, only 66-8's.
My limited research leads me to believe the 66-1 was only made from 1972-1974, then they came out with the 66-2.
If I were the OP, I'd run, not walk, back to the gun store and buy it now, if it isn't already gone. A M66 no-dash was my 2nd but longest-owned, S&W I've had. I'd love to have it back. I found an old photo I made back in 1990 when I only owned two S&W's (have neither of them today). Made the picture for insurance coverage. Lousy quality, but you can still read the SN on the card.