The engineer said that it wasn't a problem because the highest voltage
on the backplane is 5V. The manager pointed out that the power supply
was rated for 600A, and undoubtedly could source more than that
briefly, and to think about what would happen to your finger if you
had hundreds of amps flowing through the ring.
I have heard similar warnings about working on cars while wearing
rings, or worse a wristwatch with a metal strap. A car battery can provide
many hundreds of amps for a short period.
-tony