The RAAF Museum recently restored a Mossie tailwheel for its main restoration project.
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To remove the dowells at the base of the compression cylinder you will need a special tools to extract the dowells while the leg is compressed to release the load on the dowells and to release the rod...
As a retired Artillery Officer and Civil Engineer I can say I have never seen one of these objects.
The scale appears to be too coarse for artillery, you would need to be able to set angles to minutes to be effective.
It could be a means of measuring the angle of a crane Jib.
Tim
Yes you are right it is under restoration at RAAF Pt Cook. But is still several years away from completion. You can see some photos at http://www.aussiemossie.asn.au
This aircraft is actually a PRXVI A52-600 (formerly NS631) currently at the RAAF Museum at Pt Cook undergoing restoration to static display standard.
You can see more at http://www.aussiemossie.asn.au
Of interest I saw this aircraft at the same place Easter 1974!