1960s when obscenity enforcement was loosened and physique magazines began to give way to overt pornography. Beginning in the early 1960s, some magazines began to push the envelope with outlines of genitalia becoming increasingly visible through posing straps. The first appearance of frontal male nudity on American newsstands were imported European publications which bore the alibi of promoting the nudist lifestyle, which began to appear as early as 1965. The first American magazines to feature frontal nudity were Drum and the San Francisco-based Butch, both in 1966, though these led to legal challenges. Photographs were sourced from a variety of photographers and studios, such as Bob Mizer's Athletic Model Guild. Some magazines included amateur photography sent in by readers. Compared to mainstream fitness and bodybuilding magazines, which focused on highly muscular physiques, physique magazines included models with a wider variety of body types, including men with more lean, "natural" builds. Models were mostly white men, a fact which has been attributed to weak demand for photos of racially diverse men among consumers of the magazines. Models were typically young adult men in their late teens or twenties, but underage models were occasionally featured openly. For example, in 1955, Physique Pictorial used a 16-year-old cover model for its summer issue, and ran a 2-page spread of a 14-year-old model in its spring issue. Captions typically featured the name, age, and measurements of the model, along with varying amounts of biographical detail. However, these details were often fabricated to appeal to readers' appetites, and most studios allowed models to use pseudonyms. Centerfold spreads began to appear in physique magazines shortly after being popularized in corresponding heterosexual ("cheesecake") publications such as Playboy. Artwork Physique magazines often featured reproductions of homoerotic paintings and drawings by gay artists such as George Quaintance and Etienne. Famed gay artist Tom of Finland came to notice in America after submitting his drawings to Physique Pictorial in 1956, and it was editor Bob Mizer who coined the credit Tom of Finland for the artist (whose real name was Touko Laaksonen). A sub-genre of physique magazines devoted themselves entirely to physique art, such as Fizeek Art Quarterly. These magazines experienced a boom around 1963–1964. Commercial content Many physique magazines doubled as a sort of mail order catalogue. Physique Pictorial began as a venue for selling Athletic Model Guild photo sets by mail, as had previously been done through the back