Manchester City Council has replaced the existing blue plaque with a new red one, using pretty much the wording we provided.
Mouse-over the image of the blue plaque below to see the new version:
The plaque is sited on the wall of the Radisson Hotel (the Free Trade Hall as was), and is the only memorial in the vicinity of St Peter's Square. If you want to take a look it's on the corner of Peter Street and Southmill Street, here's a map.
The new plaque is red as this is the colour now used to "..celebrate or commemorate events of importance to the social history of the City..". Blue is for individuals or the building they lived in, and black for buildings of special interest. And not everyone knows that.
However this Blue Plaque in Middleton marks where Bamford's contingent gathered before heading to St Peter's Field: