having bought this one, I realized I'd seen another in recent days, so went back to the shop, and now have two.
This second example is a tad shorter at 3.5" - is unmarked and without any 'level' line, but is similar in general outline shape which is often described as a 'stopperless decanter-shaped spirit measure', and again there is a ground/polished pontil depression - pix are attached of this second example.
Quite by coincidence I was looking through Andy McConnell's book 'The Decanter' earlier today, and saw that there is a line drawing on page 447, of a measure which looks very similar to this new one - and which is described as a 'pillar whisky' measure, the smallest of which is given as a 'nip or 1/4 gill' (which is what the capacity of this one appears to be).
This is one of three line drawings, all of which are 'spirit measures from Holyrood pattern book 4, c. 1865'. I'm assuming that since legislation of the Weights and Measures Act - requiring legal standard capacities to be shown by a line on the glass - didn't come in until 1878, then this second 'pillar' measure may well date to somewhere between 1865 and 1878. I wonder how many drinkers were short changed by these unregulated measures? There is the most basic of decoration around the rim, consisting of six very irregularly spaced cuts made by a small wheel.
I know little about the Scottish factories, but having looked in the books there is every chance that this refers to the Holyrood Glass Works which was in the Edinburgh area and owned for most of the C19 by the Ford family - although the factory closed very early in the C20, apparently, with a lot of the Ford workers joining E. & L. Flint Glass Works. Perhaps someone might care to comment as to whether this sounds the same 'Holyrood' as mentioned in the book.
Coming back to the Richardson's Patent spirit measure, which was the original subject of this thread, very pleased to say that Andy McConnell's book provides some information for this one too.
A method of marking the level (on the glass) with a lead seal was patented in 1869 by W. H. Richardson (prior to the legal requirement of the Act it seems?) - son of the Stourbridge maker, whilst manager of James Couper & Sons' Glasgow Glassworks. This does add some more information about the Richardson example and indicates a date of somewhere after 1869, probably - might Stourbridge be the '35 district'??
References: 'The Decanter - An Illustrated History of Glass from 1650' - Andy McConnell - 2004.
'The Story of Edinburgh Crystal' - H. W. Woodward - 1984.
Hope this hasn't bored everyone too much