More than 30 volunteers took part in the restoration work between August 2009 and May 2010
Wales' former First Minister will unveil a renovated diesel locomotive as part of the Silver Jubilee celebrations at a craft centre and gallery.
Erwood Craft Centre and Gallery's 25th birthday will be celebrated with this event on Saturday, 3 July.
Rhodri Morgan will unveil the Fowler 0-4-0 locomotive and a historical interpretation board about the former railway station.
The locomotive has been at Erwood Station since 1988.
The project to restore the locomotive was led by the Friends of Erwood Station and started last August.
Michael Cunningham, Chairman of Friends of Erwood Station, said: "The entire project was completed by 9 May when the interpretation board arrived.
"It looks great and will always be there for visitors to see."
More than 30 volunteers rolled up their sleeves to take part in the restoration work, from rubbing down the locomotive parts like the buffers, foot plates, coupling links and sand boxes to painting the last coat on the wheels.
The locomotive has been cleaned, brushed, and painted
"When it rained we worked in the sheltered area between carriages, and when it was sunny we could paint," said Mr Cunningham.
"It was only the blistering cold of last December that stopped us.
"Rust, scrape, clean, brush, grease, TLC and team work means we now have an engine worthy of an official unveiling."
Located in the Wye Valley between Brecon and Builth Wells, the craft centre and gallery supports more than 80 Welsh artists and craftspeople.
The birthday event will also include demonstrations by Welsh artists, chainsaw carving, willow weaving, spinning, woodturning, glass making, Builth Male Voice Choir, live Welsh folk music, story telling and a Radnorshire Wildlife Trust river ramble.