What is a pattern element spare part?

In a nutshell........ its a copy of an original manufacturer spare part.

A copy element should be considerably cheaper than an original, alas, the parts suppliers dictate the price and a copy of an expensive element is kept artificially high.

An original element should come in a manufacturers bag/box/packaging, sometimes removed to package it better. The high quality of a genuine element is reflected in the price and if genuine and pattern elements were side by side its usually easy to spot the copy. Some manufacturers put the part number on the bracket, its a shame they all don't.

Insist on genuine spare parts if you want the best quality.