Can someone provide the manufacture date of a Model 29-2, serial number N146138? Also, is there a source of serial numbers and maunfacture dates similar to that for Colt and Winchester?

The 29 should be around 1973. I think Proofhouse is a source for Colts, Winchesters I don't know.

The "Standard Catalog of Smith & Wesson" book has lots of info on the numerous models produced, including S/N and dates of manufacture. It indicates that S/N starting with N100000 have an approx. date of 1973.