The set of eight medals were left behind after the parade from Shrewsbury Castle to the town's High Street after the Royal Yeomanry parade on Saturday.
Princess Alexandra, the Queen's first cousin, was there to inspect the troops.
Captain Matt Saunders, who was a member of the marching troops at the weekend, said: "I found some medals on Saturday at our Freedom parade and would like to try and find the owner. They are a very unique set of miniature medals spanning WW2 to the Cold War."
A Shrewsbury Town Council spokesman said: "Your help is needed. We've been made aware by the Royal Yeomanry that were lost in Shrewsbury during Saturday's freedom parade.
"They don't belong to anyone within the Royal Yeomanry, so it is assumed that the belong to someone who watched the parade.
"They will mean so much to someone, so please help us get them reunited with their owner. Thank you."
The owner of the medals, or anyone with information on who might own them, is urged to contact the Royal Yeomanry on 020 7384 4201 or message Royal Yeomanry on Facebook.
During the parade, 145 troops marched from the castle.
Accompanied by a military brass band and a Jackal vehicle, they made their way to The Square to await inspection from the Princess.
The parade marked the first time in which the Royal Yeomanry Regiment has exercised its Freedom of the Town, honouring the work and dedication of the Army Reservists and sealing the bonds of friendship between the town and the regiment.
Princess Alexandra arrived outside Shrewsbury Museum and Art Gallery at 2pm, where she stopped off for some refreshment before her inspection of the troops.
The special exhibition in the museum was closed off to the public until 2.30pm as the princess browsed the collection of art on display, including a watercolour painting by Turner.
In the Square, Princess Alexandra was accompanied by Her Majesty’s Lord Lieutenant of Shropshire, Anna Turner– who was dressed in a general's uniform – and Commanding Officer of the Regiment, Lieutenant Colonel Charlie Field.
On the day, Lt Col Field said: "Today we are exercising our freedom of the town of Shrewsbury and it is exciting for us as a regiment to come together.
"I am nervous, but excited, and there is a huge amount of pride; it is not often we do something like this."
Before the parade, Lt Col Field took part in a spectacle, which also served as a reminder of the civil authority of the military.
This involved banging on the Castle gates with his sword and asking the mayor to exercise the rights of freedom.
The guidon – military flag – bears the battle honours of regiments and would originally have been used as rallying points for the troops.
It stood at the heart of the procession in The Square today as it now holds a ceremonial purpose, as the 'golden thread of the regiment'.
The reserve regiment is made up of cobblers, painters and lawyers who go above and beyond their daily routine to serve in the unit, as well as holding down day jobs.
The Regiment recruits from Shrewsbury and has a squadron in Telford.
Captain Nick Trevor, said: "We are so proud and honoured to have Her Royal Highness here today on such a wonderful event.
"Being a Shrewsbury soldier myself, it's a great opportunity for the reserves and their families to be recognised for their commitment."
He best summed up a reservist's role by using a familiar quote by Winston Churchill: "The reservist is twice the citizen."