Good morning Busselton + Tony,
The study of papers on the multiple crown Wildings is currently part of my interests, and has been for the last couple of years, the one philatelic tool that I have found to be indispensable is the long wave ultraviolet lamp on a wavelength of 365 nanometres, not only can you distinguish cream, whiter and fluorescent type papers but also the different shades of ink used to print stamps plus being able to identify chalk surface ones such as the Isle of Man 3d variety, even British stamps going back to the reign of Edward Vll, there is no need to use the 'silver test' when you have this magic lamp,as the silver could leave a black mark on a mint stamp, unfortunately a genie does not appear when it's rubbed !
When purchasing unmounted mint multiple crown castles you need to know what to look for due to the massive difference in the price, so here are a few pointers in what to look for. To start with the Bradbury Wilkinson (BW) prints have a sharper profile possibly due to a higher rate of pressure when printing was taking place as against the De La Rue ones, there are several features to look out for, one of them being the earring worn by the Queen being more pronounced on the BW stamps along with the fact that the Queen's face has additional features, another point is the background above and behind the Queen's head as it appears to have more of a slant to it, the colour of the ink is also noticeable, giving a much richer appearance especially on the 10/- value, the DLR one being of a milky blue shade where the BW one is much darker as seen under normal daylight, attached are two scans of the four values in question with captions :-
A further close-up of the 5/- value gives the difference in clarity and definition when comparing like-for-like, note the hair behind the Queen's neck and the value bar at the base of the stamps, the DLR printing doesn't have the same detail as the BW version .
Under long wave ultraviolet radiation the paper when viewed from the reverse (gummed side) is of a cream shade when comparing like-for-like with similar stamps, then it will most definitely be a DLR printing, but as you are aware, whiter papers can also be found on the DLR version on being printed after the changeover date of 1962, and unless you know which is which by another method, I would tend to avoid them if possible before purchasing, below you will find a picture taken, showing the difference between a cream and whiter paper as seen under long wave ultraviolet light.
To me, the long wave ultraviolet lamp is just as important a tool as a magnifying glass or perforation gauge (if not more).
Another aspect to look for are the perforations as they are notorious for short or missing ones, make sure they comply with your standards of quality before purchasing.
For used stamps, a guide regarding first issued dates can help determine printings, especially when the date is clearly visible on the stamp and can be found below.
Issue dates as per Stanley Gibbons specialised catalogue volume 3
Denomination ___ DLR (whiter papers) ______ B.W.
....... 2/6d ......................13/07/62 ............... 01/07/63
....... 5/- ........................ 07/05/62 ................03/09/63
........10/- ...................... 30/04/62 ................16/10/63
........£1 ......................... 30/04/62 ................14/11/63
Here's hoping that yourself and others seeing this thread will be more aware of what to look out for, have a nice day, WM.