The 'sold out of service' mark in this case does not mean it was marked when leaving service. I believe this mark indicates it has been sold out of Britishicon service and into colonial (or NZ.?) service.
I have a number of British made quillon bayonets of that era that have this mark, and most have WW1 Australianicon marks present as well. I have also seen pre-war scabbards with WW1 Lithgow repairs done.
Equipment was being sent to the 'colonies' during that 1910 period and it was being marked with the SOS arrows. Much of this equipment ended up going back to Europe again with the troops to serve in the war.
The Sanderson example pictured below is interesting as it has been 'sold out of service', marked with Aussie MD ownership marks, had its hook removed during the war, but has never had the clearance hole drilled.