source <a href=httpsarchiveorgdetailsjournalofsociety18socirichpagen459mode2up>Journal of the Society of Motion Picture Engineers<a> April 1932 p455<br>シェラック盤を再生した時と Victrolac 盤を再生した時の針の摩耗具合の比較
Fig. 2. Showing comparative wearing of needles used on shellac and Victrolac records.