UNO Pencil Guide. PF3 (4.76mm) (in plastic case).
The use of UNO pens was the designated standard for use on Statutory Mine Plans under the National Coal Board and later British Coal. This and other items donated by Mr Bolton were in daily use by Mr Bolton and his colleagues at a large colliery in Lancashire until its closure in 1993.
Mr Bolton’s memories of these pens were that you had to be scrupulous in the cleaning of them in use, especially the finer sizes (eg No 1). If using them near the end of a working day then you stop working 10-15 minutes before finish time and carefully flush out the pens with running water, whilst repeatedly depressing the plunger. Final purging of the pen might require removal of the plunger wire and blowing through the barrel with your mouth and then replacing the wire. The later, spring loaded plungers, were a big improvement in design as you could routinely depress the plunger whilst stencilling to prevent clogging up. The original De Luxe, all-in-one types, were difficult to keep clog-free and the plunger wire would often buckle and become unusable if you weren’t careful or didn’t clear the nib with it at regular intervals.