Inside a glass cabinet in Tredegar stands a red card.
It belonged to Mr Prosser.
It shows the regular payments he made to the Tredegar Workingmen's Medical Aid Society.
The society was founded in the late 19th Century for local steel and mine workers to pool their resources and pay for medical care.
Aneurin Bevan used it as a model for his National Health Service.
The card belonged to Phil Prosser's dad.
It's now on display at the Tredegar Museum where Phil volunteers.
He's is proud of Labour's record, votes Labour and is a member of Labour, but he thinks Labour is finding it tough in the Blaenau Gwent constituency.
"I think it'll be a struggle for the Labour candidate to get back in as an MP" he tells me as we sit in the museum alongside his friends and fellow volunteers Jim and Gareth.
All three will vote Labour and believe the party will triumph here, but it won't be as easy as it once was when the area returned MPs like Nye Bevan and former party leader Michael Foot.
Brexit is a factor as is the growth of alternative parties. But there's another issue - Jeremy Corbyn.
"I don't think much of Jeremy Corbyn and I'm a Labour member" says Phil. "Corbyn is so far left."
When I point out that that Nye Bevan was on the same wing of the Labour Party Phil responds with, "Ahh, but he looked after his own didn't he!?"
Labour comfortably won here in the last two General Elections with 58% of the vote.
That's down from 72% in 2001 or 79% in 1997.
In the mid 2000s the seat was held by independents after a row in the local party. Plaid Cymru came close to taking it at the last Assembly Election.
Now another party thinks it can do well here: The Brexit Party.
Of the constituencies in Wales, Blaenau Gwent had the largest leave vote in the Brexit referendum.
Nigel Farage hopes he can do well with the Labour Leave vote here - traditional Labour voters unhappy with the party's stance on Brexit.
Alan is one of them.
He abandoned Labour at the last election because of Brexit. This time he's voting Brexit Party or Conservative.
"Could you imagine 10, 15, 20 years ago saying you would vote Tory?" I ask him as he sits with his Labour supporting friends in the museum.
"No. Labour has gone down the wrong road as far as I'm concerned", came his reply.
Watch the report below to see how his friends reacted to that.
Labour has a problem in Blaenau Gwent but it is unlikely to be terminal.
You still find support for the party and for Jeremy Corbyn.
A grandmother at a day nursery in the constituency told me she was won over by Jeremy Corbyn's performance at the ITV Leaders Debate. She had thought of voting for Plaid Cymru.
Another woman told me she he thought he was "fantastic, a man of integrity."
If the party lost here then it would be the biggest election-night story coming out of Wales. Few expect that.
But the election will reveal how firm Labour's grip is in one of its traditional heartlands.
Here is a full list of candidates standing in the Blaenau Gwent constituency.