Abbreviation of O.N. in relation to sailors

[Keith_history_buff]

From time to time, I see these initials in connection with sailors. Can anyone shed any light on why this appears, please? I have seen it as a prefix to some CWGC transcripts, and it frequently appears in the London Gazette too. Below is an example 

 

Quote

74. Returning, to the look-out station, [Lieutenant-Commander Bryan F.] Adams found only some wounded, but later collected two Lewis gunners and a small party under Petty Officer George E. Antell, O.N. 232634 ("Lion"). These he sent to the eastward and the Petty Officer inboard, as he had been wounded in the hand and arm before landing, and although in great pain had carried on most gallantly.

 

It did appear (past tense) to indicate they had signed up under ordinary terms of naval service. I had thought this would not appear for men of the RNR and RNVR, but it does...

Quote

The following displayed courage and coolness under fire on the nights of 11th/12th April, 22nd/23rd April, and 9th/10th May. These men carried out their duties with great steadiness, and materially contributed to the success of the operations:

Ldg. Dkhnd. Walter George Farthing, R.N.R., O.N. 2825 S.D. (M.L. 105).

Ldg. Dkhnd. George Turner, R.N.R., O.N. 621 S.D. (M.L. 274).

Ch. Motor Mech. Robert Rae, R.N.V.R., O.N. M.B. 676 (M.L. 551).

Ldg. Dkhnd. George McGee, R.N.R., O.N. 4177 S.D. (M.L. 397).

 

It also appears for ratings of the RNAS, but not for NCOs and men of the Royal Marines in the same source.

It also gets a mention on this RAN thread
https://www.greatwarforum.org/topic/167785-on-7233-flenson-stoker/

 

Can anyone shed any light on the significance of this, please?

Regards
Keith

 

 

[horatio2]

ON = Official Number

[Keith_history_buff]

So simple, yet it makes sense! Thanks Horatio!