By the time he walked into West Bridgewater Coin and Jewelry Buyers in December with a story to tell and things to sell, Robert M. Burchell had experience. He had since 2015 been caught trying to walk out of big-box stores and supermarkets with, among other things, TVs, cell phones, power tool batteries, home security cameras, a camcorder, carpet cleaning machine, chainsaw, generator, and bags of beef jerky. But now it was different. Now he was working for the New Bedford Whaling Museum with access, he later told police, to the whole place — hundreds of thousands of historical artifacts. According to felony larceny charges now pending against the 42-year-old man, he was moving onto fresh terrain with thefts from the museum, a venerable city cultural institution drawing more than 70,000 visitors last year, and even more before the pandemic. Burchell would step into the collectibles shop in West Bridgewater not once but five times in two week...