Following his severance from Selmer, in 1939 Maccaferri moved to the United States and became interested in plastic manufacturing. He produced plastic classical and steel-string guitars — of similar shape to his Selmer designs, albeit with F-holes — in the 1950s and 60s, along with many musical and non-musical plastic products. Produced first under his own name, and after 1964 under the name "Mastro", the guitars were of short scale, but accurately fretted and intonated. These instruments were not a huge success at the time and are now considered oddities. However, the many variants of Maccaferri's plastic ukulele enjoyed a considerable vogue in the 1950s and sold in large numbers.
