The heavily corroded firearm was among an array of items removed from Eric Miller’s business which sold military memorabilia.
Advocate depute Alan Cameron told the High Court in Edinburgh that possession of such a prohibited weapon carries with it a minimum five-year sentence of imprisonment.
Miller’s solicitor advocate Leanne McQuillan said he would be seeking to rely on exceptional circumstances to persuade the court to depart from imposing the minimum sentence.
Miller, 80, of Mauricewood Park, Penicuik, in Midlothian, admitted possessing the prohibited weapon at the premises of Field & Stream, in Montrose Terrace, Edinburgh, on May 23 last year.
He also pled guilty to carrying on a business as a knife dealer without having the required licence and displaying for sale air weapons without being registered as a firearms dealer.
Mr Cameron said that Miller owned the second hand shop which sold military and war memorabilia, including knives and firearms.
An Edinburgh council trading standards officer was passing Field & Stream and noticed the premises were open for business.
The advocate depute said he remembered supplying the owner with application forms for a second hand dealer’s licence but had no recollection of receiving the returned forms.
Mr Cameron said he went into the shop “with a view to establishing why he had not received the returned application forms”.
He added: “Within the premises he observed a large number of knives, swords and pistols on open view. Certain of these items clearly had price tags attached to them.”
The prosecutor said the trading standards officer was aware that Miller did not possess the correct licences for the items which were available for sale.
He contacted police to help in seizing and logging items and colleagues at the council who confirmed that an application for a second hand dealer’s licence for the premises was being processed that day, but no knife dealer’s licence or firearms dealer’s licence was in place.
A search was carried out and among the items found were nine broadswords, a large cleaver, a spear, bows and arrows, 111 swords in boxes, knives, pistols and rifles.
Mr Cameron said that various “antique” firearms that were recovered could normally be freely possessed provided they were kept as a “curiosity or an ornament”.
Air rifles, air pistols, a blank firing revolver, replicas and deactivated guns found were exempt from firearm certificate control and can normally be freely possessed, he added.
Ms McQuillan said that essential reasons for asking the judge to depart from the minimum five-year jail term for the firearms offence was various health problems suffered by Miller and his wife, and the circumstances relating to the recovery of the prohibited weapon which was not in working order.
She said that Miller acted as a carer for his wife.
Lord Bannatyne deferred sentence on Miller until later this month at the High Court in Perth and agreed to continue his bail.
The judge said: “It should be understood I am in no way indicating anything in relation to sentence in this matter.”