The 140-year-old post box is without a royal crest, which makes it rare.
It was previously located outside the Grapes pub, on Mersea Road, Colchester, before being uprooted on October 31, 2020, by Royal Mail.
It has now turned up again in Lexden Road.
Bob Mercer, of Colchester Civic Society, said: “We first noticed a box had appeared around a month or so ago, but it was ‘under wraps’ so we couldn’t be sure it was the anonymous one.
“I had suggested this as a suitable site both historically and for acceptability when servicing the box as it has a parking bay. That is why they would not replace it in Mersea Road by the Grapes.
“This has been a joint action by me, Bob Russell and Will Quince to get this resolved and it has taken years.
“It is the site of a similar box that was smashed to pieces early one morning so it is fitting to have it replaced there.”
The post box dates to 1879-87 and was a casting error by the manufacturer.
It is one of only two ‘anonymous’ boxes left in Colchester and the Civic Society says it is an essential part of the city’s history.
The other one is on the corner of Oxford Road and Creffield Road.
Eventually stock was used up and the ‘VR’ cipher was added.
Colchester High Steward Sir Bob Russell said: “It’s fantastic – Colchester Civic Society have done a marvellous job.
“It’s thanks to their perseverance and due diligence that it has been sorted.
“When I was alerted to it, I was determined to save it. It’s not its original site but at least it stays in Colchester, even though it should have never been moved and it took a lot longer than we wished.”