One nice big industrial thermometer. gov surplus, they probably replaced with electronic, as these all look to be in excellent condition. Has red fluid (not silver!)These as many higher quality thermometers are unique, in that you have to look at them straight on to see the indicator bar/not visible from side angles. Many uses: Boilers (not on the hot water side of unit as this only goes to 100! ) hot water heaters (not on the hot water side of unit as this only goes to 100! ) Kitchen equipment HVAC equipment Works by itself even if not mounted in a boiler You can mount the thermometer outside your window for accurate temperature that never needs a new battery! Or drill a hole in your wall so the sensor end goes outdoors but indicator is indoors. You can also just set it on a shelf and get accurate indoor temperatures. Outer diameter of threads is approx 1.25 inch Pict is a sample, all have light signs of use/handling etc, may have small scuff, marks, or have pipe compound residue on threads. We have lots so ask if you need a larger qty than shown Not sure of model # as filled in # based on a similar listing, but selling ones like shown.