REFERENCE: RARE FINNISH BAYONETS (NOT FROM MY COLLECTION)
Fiskars:
Blade is always type m28-
Hackman:
Without oil hole: always M28-
With oil hole: about 1800 made with M28-
Earlier bayonets, made only by Hackmann, had M28-
Later Hackmann and Fiskars made bayonets had their own M28-
(Thanks Tuomo Järvinen for data and pics)