The Main Roads marker is in Rosewood on the road north towards Tallegalla, marking 1 mile from a survey point.
Mile markers used to be a common feature along roadways, marking distance along roadways from a location called the zero point. Mile markers from Sydney were measured from the historic Macquarie Place Obelisk , designed as the zero point for measuring roads in colonial New South Wales from 1818.

More modern versions can still be seen showing how many kilometres remain to the next town (or how many from the last town, depending on the state). They are metal signs on posts like most modern signs are.
These too have become less popular over the years. I don’t think they (the modern versions) are officially used anymore but occasionally I see them on the side of a highway or country road.
The older original style, like this mile marker in Rosewood, are all but gone.
There isn’t much to the location other than the marker itself. It is on an otherwise ordinary street corner and if it did not have a brown sign above it we’d probably have driven passed without noticing on our way to Tallegalla Cemetery .
The information on the sign at the Belmont Estates marker has the following:
This post is an Main Roads Bench Mark. The markings on the post indicate that it was 1 mile from the starting point of the survey and its elevation was 254.41 feet above State Datum.
As time goes on these posts are gradually disappearing. This post was Restored and resurveyed by Ipswich City Council workers, on 28 September 2001.
The post was originally placed on 8 May 1947 by J. Butcher on behalf of the Main Roads Departments.
It is not known if this person was an employee of or a contractor to Main Roads Department.
Cr David Pahlke, December 2001.
To Get There

The Rosewood Railway and Kulkana is on Scenic Rim Tourist Drive 16 between Rosewood and Marburg.
From Rosewood, head north on John St and continue straight at the roundabout. Follow for another 400m and the road bends to the left becoming Waight St. Continue anther 150m and the marker is on the left on the corner of Waight St and Albert St with the brown sign above it.