When you hear the words "Pre-86" in conjunction with NFA, the connotation means "dealer sample". Prior to 1986, they were simply known as "dealer samples". In 1986 the rulez changed and an imported foreign made or U.S. newly made gun became a "Post-86" gun. They are still dealer samples with the only real difference being a "love letter" being necessary to purchase and if you leave the bidness, all "Post-86" samples must be disposed of (destroyed), turned into ATF or sold to other SOT dealers. "Pre-86" guns may be retained if the owner is a "sole owner" of the SOT license.
In your case, pre-86 will merely mean transferable. HK never made any sears... just full auto guns. That said, Fleming made a run of god knows how many Post sample sears recently that only an SOT dealer or manufacturer can use, pictured here.
Not to be confused with this...