Bently Nevada 21508-02-12-10-02 appears to be an 8mm Proximity Probe belonging to the 7200 Series. Here’s what I found about its technical specifications:

Key features

• Model: 21508-02-12 – 8 mm Reverse Mount Probe
• Cable Length Option: -10 – 1.0 metre (39 inches)
• Frequency Response: 0 Hz (DC) to 10 kHz
• Noncontacting: Operates without physically touching the target
• Gap-to-Voltage Transducer: Measures changes in distance (gap) and converts them to voltage output

Additional specifications (may vary depending on source):

• Probe diameter: 8 mm
• Operating temperature range: -40°C to +200°C (-40°F to +392°F)
• Output voltage range: 0-10 V (typical)
• Material: Stainless steel
• Mounting: Reverse mount
• Weight: Approximately 0.1 kg (0.22 lb)