I do not think this is any typical symbol. Probably a tribally understood symbol within the organization that drew it. But maybe it leaves enough clues to figure out what it means. Sorry, the following isn't going to be very coherent, but just take it as a series of clues/possibilities.
The drawing says (paraphrased) that T1 is the same as T2 thru T9. Under T2 thru T9, they are listed as PT100 temp sensors. I am 90% sure that the sensor in question is a 3-wire PT100 sensor. But the rest of the symbology is a mystery.
I have seen some symbols on PT100 sensors which look almost like a pound sign:
Maybe the system which generated the schematic was incapable of drawing the "half-pound-sign" like in the above image, so they substituted the pound sign.
As for the "//" the first thing that comes to mind is "parallel"
Maybe parallel means in a bridge configuration. That is done sometimes, like a wheatstone bridge:
maybe it is a niche industry symbol. Here is an image taken from a
**broken link removed**:
**broken link removed**
They are apparently using "#" to mean signal ground or something. And there is a resistor in parallel, maybe that could be expressed as "//"
Sorry that's all I can think of...