It was North Tees Colliery :-
http://www.dmm.org.uk/colliery/n004.htm
Born & bred in the area , as lads we used to get on out bikes & go off to OCCS to watch the plant working esp. drag-lines , I do recall cadging rides on Vickers Vigor but don't recall Sherman.
Often strip-mining (as well as restoration work) with box-scraper was used at old Board & Wall pits to get at stacks (pillars of coal left holding the roof) , some fields had props holding corrugated sheets up only 6ft or 8ft under the surface.
My memory serves me bad here , ISTR that North Tees was in fact Long Wall mining & that miners were seen walking to & fro in full kit as late as 1968 , leading me to think that when the NCB pulled out it was private underground mined by the under 30 man rule and then strip-mined . I would therefore guestimate those photographs at abt. 1970 or very early 1970's , don't recall any box-cuts there involving drag-lines at all. Unfortunately - in mid 1970 I went off to sea as a Junior Engineer , so would not have been around .
Hutchinson is a common local name , I guess Ian Huthinson is / was related to the Hutchinson family who built & still run a garage The Mickleton Service Station - I guess they may be able to tell you more..