I have applied for a US patent “Combo Depth Gauge”
This is an old capillary depth gauge, but it is designed in such a way that it allows you to adjust the accuracy of the scale within the desired range.
The simple design and technology makes it possible to obtain an inexpensive, but accurate and reliable device. It can serve as the first depth gauge for beginners and as a control and back-up device for the experienced divers.
Using my own funds, I made the tooling and a batch of parts for the production of a pilot batch of my depth gauge.
Currently, I can supply for sale a pilot batch of 200 depth gauges called Mark 25. You can buy such a depth gauge directly from the author of the invention on my website. I think that the first batch can immediately become a collector's item and the depth gauge you buy will remain in your collection.