I have just acquired a very nice looking process lens, can anybody shed some light on it?

Where/how used etc?
History?-

I bought it as a possible user on an 8x10 enlarger but am know thinking it might not be big enough-

its glass is sparkling but the iris doesn't open right up- ie- to the outer edges- it does open to all the correct dial marks etc - but at full open , it is still half shut-

most curious!-