You have only provided a generic description. Trying to put a value on anything with just this limited information provided is difficult. Value depends on a combination of many factors. Without a detailed description to include, finish, barrel length, overall condition, stock material, sights, box, original paperwork and any accessories, only a general estimate can be given. This weapon could be in the 100-750 USD price range.
50-600 usd
Standard Catalog of Smith and Wesson, 3rd ed.
Your serial number indicates that your Smith and Wesson model 29 was made between 1977-1978.
What serial?
100-650 usd
50-2500 usd
1994
@ 1980
100-1000 USD
The Model 29 is a 44 Magnum.
No such model in S&W line. Model 29's can range from 100-1000 USD
An engineering change.