Maybe check with others, but one way to get a signature to stand out is to dust it lightly with talcum powder, you could try this on the engraving - though it might be inadvisable on an important surface - see what others say befor you actually do it!
I met Denis Mann at a Scottish Glass Society exhibition in Crieff a few years ago - lovely gentleman.
This is a picture of one of his engraving I took at the time.http://i20.photobucket.com/albums/b227/chopin-liszt/wave/SGS/DenisMannDancerheroine.jpg
Sadly, I didn't get an image of the engraving I found most interesting, and I had a nice discussion about it with him.
It was called "Duet", it was on a cobalt blue background.
It was of two hands playing the piano, but when I looked carefully at the notes, I could see it was a nasty discord the fingers were actually placed on - so I asked him about it.
He then pointed out to me that one hand was female, the other was male.
So not only a wonderful engraver, (and a lovely friendly man) but there can be more to his work than you might first think.
The shape of the glass your engraving is on is not a new piece either - this dates to the time of Domnail o'Brien's decanters. (I've got a matching set, with small glasses, in purple and clear glass.)
(Two wineglasses with a purple cup part have just sold on ebay in the states for ~£40.)