What is this wrench for?

[rwremats]

Anyone know what this wrench may have been designed for?  I can't figure out if it is for spark plugs or howitzers.  It is a heavy duty wrench being about 3/8" thick.  The wrench sizes are 1/2" and 5/8".  No markings on the other side except the number 72 being stamped on it.  I appreciate any input.  Thanks.

[rusty]

>> I can't figure out if it is for spark plugs or howitzers

howitzers is half way there...

The watertown arsenel 1905 annual report shown an entry for "wrenches for filling plugs and filing pin points"
The entry is for supplies for 75mm Vickers-Maxim Gun carriage.

Sadly, the wrench size is not given.

"Filling plugs" comes with a note that they are leather washers...(??)

"Firing pin points" seems to refer to the lock pins on the firing handle attached to the carrage, this term is not common...

Assuming my wild guess is correct, it should fit something that looks somewhat like this:http://en.wikipedia.org/wiki/QF_2.95_inch_Mountain_Gun

[rwremats]

That is great info.  Thanks for your research and I appreciate it.