Help deciphering Naval list entry

[steveflan]

I found out recently that my great-grandfather, William Holden, was awarded the DSM for his service with the Mine Clearance Force during the First World War. I'm very glad to say that subsequent inquiries have confirmed that the medal still resides with a family member, and am currently looking to get agreement from other family members that it remains in the family in future generations and is not sold on.

However my question concerns his London Gazette citation. He is listed as:

P.O. William Holden, O.N. 237251 (Dev). in Edition 31604 of the London Gazette.

I am assuming that P.O. stands for Petty Officer, and that the O.N. entry is his Naval 'service' number.

Can anyone let me know what the O.N. stands for? (I am also assuming that the N stands for Naval or Navy), but what does the (Dev) mean? Is this some kind of shorthand for the Naval equivalent of a Territorial force?

Many thanks in advance.

[daggers]

P O is Petty Officer, O N is 'Official number', Dev is Devonport, one of the Royal Navy's main manning stations. Others were at Portsmouth and Chatham I think.
Good luck with the medal - fine memento.
D

[MaryA]

Lovely to have a medal like that in the family, I hope you get the assurances you want for it to remain with his descendants.

[steveflan]

Thanks for the clarification Daggers - much appreciated.

As you and Mary say, nice to find that his medal is still in the family.