Caselli thermometer, mercury in glass with a long slender stem and a bulb at one end, the bulb is filled with mercury. The stem is marked with a scale that indicates temperature. I haven’t been able to identify tjhis thermometer exactly by the unit number. There are still a good number of jourmals / catalogs available on the internet, which should help. Caselli was a large company, producing many types of scientific instruments. If anyone knows about this particular model, I’d really appreciate if they would share this with me. If you are in London, we could meet on North London. Any questions, drop me a note or 07811 216111.