Exact item shown, these are older but from all appearances unused Platinum RTD sensors for air temperature, these are generally used in a laboratory, I got them with other surplus that I could date to the 1980s or 90s, and that would explain the faded labels.  I spent way to long trying to figure these out exactly, the very faded label didn't help, as you can see from the images I read it as RFD-805, but I am quite sure it is RTD-805 based on the catalog data below.  I measured the room temperature resistance and it was about 1100 ohms, and the standard RTD-805 in the catalog says it's a 100 ohm device, so that puzzled me for a while.

The Omega data sheet for the RTD-805 is here 

https://assets.omega.com/pdf/test-and-measurement-equipment/temperature/sensors/rtds/RTD-805_RTD-806.pdf

Here is a snipped from the Omega UK catalog, confirming that the specific staniless shield shape belongs to the RTD-80e series.

Air and Gas Stream Measurements Air and gas stream measurements are a challenge because the rate of transfer of temperature from the fluid to the sensor is slower than for liquids. Therefore, sensors specifically designed for use in air or gas place the sensing element as close to the media as possible.

OMEGA’s RTD-805 and 806 sensors allow the sensing element to be nearly in direct contact with the air stream. With a housing design containing slots that allow the air to flow past the element, this construction is very popular in measuring air temperature in laboratories, clean rooms, and other locations.

I took resistance measurements, it is a three wire system, the red dot marks the "red" wire in the system, and the other two prongs of the plug are "black wires" used in a Wheatstone bridge configuration to cancel out the resistance of the lead wire. I measured about 1100 ohms as noted above, breathing on the sensor caused the resistance to rise a few degrees, so they are working.   So now that I had a pretty good idea of what I had I asked Chat GPT to tell me what it's spec was - and based on my measurements and catalog reading this is pretty accurate.

The part number Omega RFD-805-F2020-1000-1000A appears to be a combination of two components:

1. RFD-805: This is likely a model from Omega's RDF series of compressed air dryers. These dryers utilize a three-stage heat exchanger system to efficiently dry compressed air. The RDF series includes models with varying capacities, such as RDF 20, RDF 35, RDF 50, and so on, each designed to handle different flow rates and applications. 
2. F2020-1000-A: This refers to an OMEGAFILM™ Flat Profile Thin Film Platinum RTD Element. These RTD elements are designed for OEM applications and have the following specifications:
• Resistance: 1000 Ω at 0°C
• Temperature Range: -50°C to 500°C, depending on accuracy class
• Tolerance Classes: Class A, B, and 1/3 B (also known as Class AA)
• Temperature Coefficient: α = 0.00385 Ω/Ω/°C nominal
• Self-Heating: Does not exceed 25% of the tolerance value when powered at the maximum specified operating current
• Response Time: Water current (v = 0.4 m/s): t₀.₅ = 0.2 s; t₀.₉ = 0.4 s
• Lead Wires: Platinum-clad nickel wire leads, 10 mm length x 0.2 mm diameter 

If you're seeking a specification that matches the part number RFD-805-F2020-1000-1000A, it would be a combination of the RDF series compressed air dryer (RFD-805) and the F2020-1000-A RTD element. 

If you look up the part in the Omega catalog, they are $209 each.