My cylinder release button is the old full size,I've seen some with the new type that is smaller.
My serial number is BUF4963,I think a date of 1995-6???.
When did they change to the new style?
Anchors,
On the 686 they changed with the -5 version. Not real sure about the 640. My wife's new 638-6 had the new one, and my 649-3 also had the new one. If you'd like the new one i have a spare one SS here that i'd be willing to simply swap you if you have the older SS one.
Carl