Therefore a welder is qualified to Maximum/Unlimited thickness if said welder successfully welds a .500" (13mm) thick or coupon utilizing a minumum of 3 weld passes with ONLY one process and SAME F number.

I have never come across such a WPQ. The only instance where I could see this being used (in the real world) is the use of E6010 root and E7010 HYP remainder being used in 1104 pipeline welding. Same F no. and same process.

I am more familiar with the use of E6010 root and E7018 rem but that wouldn't qualify for unlimited because of two different F nos. Or the use of GTAW root and SMAW remainder wouldn't qualify for unlimitied because of the use of two processes.

Can you think of any other situations?

See clause 1 in Notes below the table .

I understand Note 1, what I am asking is what specific single electrode would be utilized to weld the coupon?

Hello sooeey2u

Please read the code carefully. No single electrode is required to qualify the test coupon. You can do the root welding with the same elctrode or filler wire you are going to use in production joints and complete the coupon with the second electrode. Only thing to be taken care is to select a coupon having adequate thickness, such that the weld deposition of a minimum 13mm can be achieved with the second electrode alone.

Aztig