It's not an amateurish question at all.
The Mayking Test pressings were generally the very first pressings done at the pressing plant. Pressed from the metal master plates, these were pressed in small numbers (typically 3 - 10), had their own Mayking Records labels and would then be examined and played at the pressing plant to ensure their quality. They would then be passed on to the record company to make sure that they met with their approval. Once the record company were happy with them, full pressing production could commence. Even then, further test pressings could be run for various reasons but these would normally be the plain white (or green, yellow, pink, red, purple or whatever was available!) labels. It is worth noting that Rough Trade, (like most independent record labels) wanting to get their money's worth, often used their approved test pressings as promo copies, sent out to radio stations, music publications and reviewers. These were generally pressed in greater numbers than the Mayking tests.
I've probably made the whole process sound a bit simplistic. Stephane (if he is around) would probably be able to explain it better.