A Victoria Cross (VC) medal awarded to a Tasmanian Sergeant after World War I is tipped to fetch more than $500,000 at an auction in Sydney this week.

A bugle that was played during the Gallipoli landing nearly 100 years ago is also among the memorabilia set to go under the hammer.

The VC Medal was given to Sergeant John Whittle in 1917 for "conspicuous bravery and devotion to duty on two occasions" in France.

Auction house managing director Jim Noble said Sergeant Whittle was a career soldier who also served in the Boer War.

His platoon suffered heavy casualties during World War I as the enemy was preparing to attack with a machine gun, and his VC citation said he "rushed alone, across the fire-swept ground and attacked the hostile gun crew with bombs before the gun could be got into action".

Mr Noble said Sergeant Whittle was "just one of those true Aussie heroes".

"He made his decision to risk his life, killed quite a number of the enemy at great risk to himself, probably thinking he wouldn't survive it, and just did his duty," Mr Noble said.

Sergeant Whittle's heroic actions were not limited to the battleground.

A bugle used by an unknown soldier at the Gallipoli landing. ( ABC News: Nicole Chettle )

"He rescued a boy who was drowning in a pool near Sydney University, [then] walked away," Mr Noble said.

"It was only two days later that they found out who it was that rescued him."

Mr Noble said there was plenty of interest in the medal from private collectors, and he hoped it would be displayed in a museum or at the Australian War Memorial.

"There's a collector in England who doesn't own an Australian VC. I was thinking it'd be nice for him to buy it," Mr Noble said.

"He can't take it out of the country, but he could leave it in a museum."

Historic auction items valued at more than $6m

A bugle carried by a member of the 2nd Brigade at the Gallipoli landing in 1915 is expected to sell for $15,000.

A shield attached to it reveals the bugler was wounded on the day of the landing and later died.

The war medals of Private Horace William Madden, who was posthumously awarded the George Cross, are tipped to fetch $250,000.

Private "Slim" Madden died of malnutrition as a prisoner of war in Korea, and famously shared his meagre rations with other soldiers.

The war medals of Private Horace William Madden, who was posthumously awarded the George Cross. ( ABC News: Nicole Chettle )

"He was in captivity and wouldn't give any secrets away under torture," Mr Noble said.

"He was starved, but rather than taking the food himself he gave it to his starving mates and he died doing that.

"He was awarded the George Cross posthumously - the only Australian to receive such an award in the Korean War."

The auction also includes copper coins known as convict "love tokens".

One dated 1797 says "forget me not" and "liberty is sweet".

"These were engraved in the earliest days of settlement by convicts who were travelling to Australia," Mr Noble said.

"The only way you could get a record or memory of your loved one was to have this copper coin shaved down."

One token, dated 1844, features a ship engraved alongside a kangaroo and an emu on a smoothed penny.

A message on the other side, from a convict to his father, said: "Accept this, tho' poor it be and keep it for my sake ... may your kind and grateful heart no more have cause to ache."

Del Parker, a buyer's representative from Dallas, Texas, said the Sydney auction was "the clearing house for the southern hemisphere" when it came to world coins.

"Now we have people making more money than we can dream about spending collecting things ... to map out the world," Mr Parker said.

"So you want to have key items."

The auction of nearly 5,000 lots is open until Thursday and is valued at $6.5 million.