I purchased a pocket-gamma spectrometer last week (Radiacode 102) and brought it with me to a local flea market to find some radioactive antiques! I also found a radioactive gimbaled compass in a box, but did not buy that one.
Here is the processed Gamma spectrum measured with the Radiacode:
Photo with lights on:
Radiacode placed against it:
Yes, the gamma emission peaks correspond to specific transitions of excited nuclear states or to processes such as the annihilation of an electron and a positron.
The app has a built-in database of common decay chains, so I can click on a peak and lines are drawn at the positions that correspond to the radioactive chain. In this spectrum one can see primarily the lines from the decay of radium-226 and its products lead-214 and bismuth-214
Here is a labeled spectrum I found at https://www.gammaspectacular.com/blue/ra226-spectrum :
awesome