A short quote from Susan Tobin's 'Wedgwood Glass' 2001, page 76...
Re etched wedgewood mark in upper or lower case...
"This mark is found only on items designed and produced during the association between *Wedgwood Crystal and Dartington Glass. It appears on the base of items designed by Frank Thrower. (Some of these items bore not only the word 'Wedgwood' but also an alphanumerical inspectors code, eg A/I, B/I, C/I.....)"
*1982-86