Although the ad states that the booklet is for the Model 39, which the gun did eventually become, this booklet is not model marked and was actually for the pre 39. This should not be confused with the traditional 4 page parts lists that came out post 1957-58 when the government required gun manufacturers to model mark their guns.
This gun was produced from about 1954 to around 1982, so the non model marked brochure was only used for a few years before the model marked ones appeared. The later ones being issued for a period of about 25 years. There are fewer of the first brochure in existence and therefore the price reflects the rarity.