The 982, according to what I could find, was produced from 1935 to 1952 (with modifications during and following WW2.

770 from 1956 to 1969.

987 from 1924 to 1948, but with variations. The first (to 1929) had semi-friction balance jewelling. Them an improved version with improved friction jewelling for the wheel train was introduced.
Now don't ask me to explain that, but go to our old friend google to find http://vintage-hamilton-wristwatches.com/2012/10/hamilton-987-movement-variations....., by Tom Adelstein. The article gives clear pictures of the models.
Adelstein considers his 1938 Martin a bargain, compared "to $5000 + wristwatches made and sold today."

From the Price Guide-
Martin, c. 1941, gold-filled coral (rare) $125-$225. Gold filled yellow $75-$125.
This and all other models are in demand, so expect a good one to sell for at least three times these 2011 catalogue prices.