Look here:
Valkyrie Factory
The Alpha is the 1/55 3 mode version and it does contain a small amount of die-cast.
The one pictured in the auction appears to be a bootleg as the feet and chest are silver and the plastic is looks to be of low quality and slightly off color compared to the normal Gakken release. It is also possible that someone scraped the paint off the toys feet, exposing the metal underneath.
I'd be interested to know if the Gakken name appears on the toy.