I used an app on my phone as a basic check on its operation, and the frequency I recorded was spot on, at 1000Hz, which ties in with the frequency on the label (see screenshot from my iPhone).
eBay
SMART SENSOR AR884A Sound Level Meter with Large LCD Screen Wall Mounted Digital Sound Level Meter Noisemeter Monitoring Tester
Aliexpress UK
CASELLA CEL-254 Digital Sound Level Meter Tested working (114dB at 1kHz) Local collection: SN Electronics Gloucester Delivery charge: May vary if outside Europe
eBay
3 Inch Large LCD Screen Wall Mounted Digital Noise Meter 3.5mm Sound Cable 30-130dB Range Sound Level Meter Tester for School
Aliexpress UK
We reserve the right to substitute an alternative of similar specification at our discretion. Level range: 30 – 130dB. IEC 61672-1 class 2. Dymamic 50dB.
eBay
MASTFUYI FY826B Digital Sound Level Meter 30-130dB Decibel Portable Noise Audio Level Sonometer Meter for Environmental Testing
Aliexpress UK
Model: 407744. Battery test position with battery status LED indicates if battery is good. Durable die-cast aluminum housing generates a 1kHz sine wave at 94dB to an accuracy of 5% (frequency) and ±0.5dB (94dB).
eBay
VU Meter 2 Pcs Panel VU Meters Warm Back Light Analog DB Sound Level Indicator Recording & Audio Level Amp with Driver Board
Aliexpress UK
15 minutes of inactivity. Operation Temperature: 0 to 40°C [32 to 104°F]. Digital Display: 3-1/2 digits. Display: LED. Alarm Function: "OL" is show when input is out of range [>130dB] "Un" is displayed when the input is less than the range [<30dB].
eBay
35mm Panel VU Meter 500VU with Green Backlight sound pressure meter+VU level audio meter driver board DC/AC 6-12V input
Aliexpress UK
It has two heavy duty or alkaline type, DC 9V batteries (006P, MN1604 PP3). Sound pressure level range from 94dB and 114dB. Sound Level Max 114dB. Sound Level Min 94dB. During that process you will be issued with an RMA number.
eBay
MASTFUYI Digital Noise Meter Sound Level Meter Handheld DB Meter A- Weighted 30~130dB Audio Measuring Instrument Decibel Monitor
Aliexpress UK
eBay
GN102 Noise Meter Sensor Sound Level Meter 30~130dB A weighted DB Meter Portable Tester Audio Measuring Decibel Monitor Tools
Aliexpress UK
Supplied with carry case. The item has been tested and is in good working order.
eBay
Sound Level Meter Audio Visualizer Audio Spectrum Analyzer Real-Time Sound Monitoring 10x16 High-Resolution Display
Aliexpress UK