I used to live in Tuffley Avenue as a child and both this and the adjoining vacant sites were prosperous industrial areas when I was younger.
Planning records show that the Wellman Graham site has been in use since at least 1944 for heavy engineering by Barron and Sons, then
Simon Barron, before Wellman Graham. Historic maps show an engineering works on the site in 1936.
The spooky thing was that whilst doing a little research on this site I found that a Planning Brief by Gloucester City Council for future development of this Industrial site in Bristol Road and the adjoining area in Tuffley Crescent was approved by Cabinet on 11th March 2003 - exactly 10 years to the day that I placed the cache here on 11th March 2013!
You are looking for a small magnetic container, with log and pencil.