Abbey Road Studios - Lester Smith, Abbey Road's microphone custodian, takes us through the STC 4021: “We know it as the 'Ball and Biscuit' and it was manufactured from the early '30s
Lateral Science: Apple and Biscuit Microphone for Acoustics Laboratories - the STC 4034
STC 4035 Ball & Biscuit Microphone | Reverb
STC 4021A Antique Ball & Biscuit 1930's Microphone for Sale in BLACKBURN, Victoria Classified | AustraliaListed.com