Police photographed the bomb once it was declared safe. Mr Paterson said the bomb was almost chest height.
It was identified as a US training bomb from WWII.
"They still explode. This type had two fuses and that apparently causes problems when untrained persons try to defuse them," Mr Paterson said.
Police believe the person who dumped the bomb knew it was inert. It was very clean and may have been passed down at least one generation as a "trophy".
"These people should have called us or our arms officer to discuss disposal options, the service is free," Mr Paterson said.
Anyone who found anything resembling a bomb should leave it exactly where it is and call police. Anna Leask