The document reworks and broadens the definition of what parts constitute a regulated firearm receiver. It then says any unfinished part that “may readily be converted” into a receiver must be treated as a receiver and requires sellers to obtain federal licenses, mark the unfinished parts with serial numbers, and perform background checks on buyers. The proposal provides only subjective standards for what makes an unfinished part “readily” convertible into a finished firearm but provides footnotes to court cases where the term has been applied. One court example included in the document said a part completed in “around an eight-hour working day in a properly equipped machine shop” was considered “readily” convertible. The only example of a ruling defining when a part is not “readily” convertible involved a process that “required [a] master gunsmith in a gun shop and $65,000 worth of equipment and tools.”