I would imagine Mark Hill's statements are the most accurate available, given he worked with the Harris family to write his book, and it has their seal of approval.
However, I think Andy's comments probably refer to Michael Harris' resistance to putting his own signature on pieces, unless it ws specifically requested.
Elizabeth Harris also told me, some years ago, that he sort of lost interest in a piece as soon as it was finished - he was simply so eager to get on and see what he could do next, in the true spirit of the family slogan - "Our best work will be done tomorrow." He was a complete workaholic.
I believe certain ranges were signed by him, at the specific request of some American import companies - and a lot of the "Rosenthal" range was signed because of this, despite the fact that the major order never really came to fruition.
I believe the paper labels were used both before and after he left. Sometimes there are rectangular labels with numbers written on in biro - these refer to order numbers. The label is sideyways long, rather than upright.
I have also noticed that most of the "Japanese" globe vases are signed by him.
(I have also noticed that these are cased/made in a very similar way to the Fish vases - side-dipping, then twisting to catch the trail, which ends up crossing over between the dipped sides!)
Going over my collection some time ago, I started to try to catalogue all the various scripts used, but then I got ill, and all the lifting, shifting and bending became impossible, but I'd identified over 25 different kinds of handwriting, and it's very much all in the same time frame as the pieces in Mark's book. I hardly have any of the "splodgy" stuff, which was not Michael Harrris' design - I think that was Joseph Said, as are the seahorse PWs.
Basically, absolutely nothing was set in stone or standardised. You have to date the glass by the style and the shapes and the colours.
It was the late '60s, hot glass worked by individual artists in small studios was a new and exciting medium, Michael Harris was more interested in learning what he could do with it than regulating marks on it.
I would love to be able to put the images in glass gallery, but I simply cannot resize them - I'm a technodinosaur - I can't follow all the steps of how to do it, (short-term memory problems as well as a body which doesn't work properly - I've got ME) which is why I use photobucket.
(I can't put pics in the middle of threads either, sorry)
But if anybody can use the photobucket images to put them in the gallery, that's fine by me!