Still trying to understand what I have. So you're saying Browning didn't make a pre war commercial ? If post war with slot (Im sure they would offer stock for the slot} this hollister and backboard would be illegal is some states being considered a short rifle. Looking to find out law on this,I stumbled on this
SECTION III: Weapons Removed From The NFA As Collector's Items And Classified As Curios Or Relics Under The GCA
The Bureau has determined that by reason of the date of their manufacture, value, design and other characteristics, the following firearms are primarily collector's items and are not likely to be used as weapons and, therefore, are excluded from the provisions of the National Firearms Act.
Further, the Bureau has determined that such firearms are also curios or relics as defined in 27 CFR 178.11. Thus, licensed collectors may acquire, hold or dispose to them as curios or relics subject to the provisions of 18 U.S.C. Chapter 44 and 27 CFR Part 178. They are still "firearms" as defined in 18 U.S.C. Chapter 44.
Any military bolt action or semiautomatic rifle mfd. prior to 1946 and accompanied by a "cup type" grenade launcher designed for the specific rifle. Belgian, Pre-war mfd. Hi Power pistols, in cal. 9mm having tangent sights graduated to 500 meters, slotted for shoulder stock, having S/Ns of less than 47,000 without letter prefixes or suffixes and accompanied by original Belgian mfd. detachable wooden flat board type shoulder stocks.