@Franklin Halves: Here's some additional information about your medallion. Hopefully. you'll find it useful/interesting.
The Massachusetts Bay Tercentenary medal that you've posted was produced/sponsored by the Massachusetts Bay Tercentenary, Inc. It is considered an official medal of the statewide celebration; there are many other official medals for individual towns/cities.
The side with the codfish and anniversary inscriptions is considered to be the obverse, the New England development scene (from initial landing of pilgrims to skyscrapers and airplanes) is the reverse. On the reverse, the figure at the bottom center is John Winthrop. He was a key figure in the Massachusetts Bay Colony's founding and was its first governor.
The Tercentenary Medallion (as it was called) was available in three finishes: bronze, silver and gold. Note that I said finish, the medals were not solid silver or gold. The issue price of the bronze finish piece was $3.00, the silver finish piece cost $4.00 and the price for the gold finish medallion was $5.00. During the initial ordering/delivery period, only one of the three medals could be ordered but multiples of the medallion in the various finishes could be ordered for later delivery. The medal came in a box with a small leaflet describing it; I am unaware of the booklet about the medal that you mentioned, but it's certainly possible that one was produced.
As you've noted, the piece was produced by The Robbins Company of Attleboro, MA. The company produced several medals for the tercentenary, but none as large or as impressive as the one under discussion. For those viewing the medal via images, it is approximately 2-1/2 inches tall by 3-1/4 inches wide.
Shepard Pond (the man who literally wrote the book on Massachusetts Bay Tercentenary medals in the 1930s) has reported that 2,000 of the medallions were produced, but did not specify how many of each finish. The medallion was also available as a uniface piece mounted on a wooden plaque; 400 of these plaques are reported to have been produced.