Was the R410a system in a vacuum? If not, wouldn't the R410a pressures have exceeded the pressures in your R22 gauges?
There is nothing more frightful than ignorance in action....Mark Twain
A new manifold set has R-410A,R-404A,R-22 markings.
Manufacturer says using on any of these refrigerants will not contaminate the system. I would guess they want you to empty your lines after checking pressures and before going to a different system.
Anyone seen these. I saw them at Sid Harveys.