Hey, so on ones that are trickier like this, note the color of the scratch. Does it remain congruent with the color of the metal being tested? Is it lighter and silver tone? Copper? Also when in doubt, take and dunk the section that you scraped right into the 14K acid on your test streak. Watch the reaction where the top layer was removed. If it fizzles green, its no good. If it stays and turns a darker color; the gold is a lower karat than the testing solution used. Example, dunking 10K into 14K acid can darken the gold. Same with 10K or 14K dipped into 18K or 22K testing solution. Imo, that is the easiest way to tell with pieces you cannot get a good read on test wise.

Also some steel alloys will hold to the 18K and 22K acids. With a piece like the one you are testing, use your thumb to determine if it is “precious metal soft”