Am new to these guns but want to buy one. Needs to be over 50 years old to purchase in California. Understand significance of flat latch and have a list of S&W serial numbers tied to dates of manufacture.

However, I am unclear what the significance of "no dash" is. Does it allow someone to be sure about date of manufacture, and if so, what dates were the no dash version made?

Can't wait to get one of these beauties.
Thanks!