This is the bike in question, but I am not sure just what brand that stem is.
Could it be a Nitto?
Zenith when you get your PB blaster spray some on the BB area too. It looks like these cranks have a 'single key release' or selfextractor system. if you want to remove then you a type of Pin Spanner that has two flat areas rather than pins.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk