source <a href=httpsarchiveorgdetailsjournalofsociety18socirichpagen459mode2up>Journal of the Society of Motion Picture Engineers<a> April 1932 p454<br>Victrolac 12インチレコードと通常の16インチレコードとの比較
Fig. 1. Relative size of standard groove on 16-inch record, as compared with the new groove on the 12-inch record.