There are 2 glyphic variations of "眞" in 説文小篆. "海源閣本", as a sample of 宋刊小字大徐本, show non-standard shape at 4 entries. The same entries in 南宋板説文解字五音韻譜 show non-standard shape. Of course, 小徐本 does not show such non-standard shape. Does it mean that 宋刊小字大徐本 and 五音韻譜 shared the source material?