Sorry... I have had no time to look for details of the ship... BUT I think the ship types folders tree in Shipspotting is not the most proper one in general (classification / categorisation is not always proper.. sometimes "naive" or not logical, not to mention it is not close enough to professional categorizations)...
..and dividing one ship type category into so many, so relatively short, periods is useless and troublesome... the border points (boundaries) between subsequent time periods might be also discussed as questionable ones (taking into consideration the history of technical and market development of ships)...

I am looking forward towards automatization of Shipspotting and its integration with ship databases... then little effort of providing IMO no. would be enough for most uploads and would solve the problem of lazy or busy (not having enough time) uploaders / contributors... I may declare I will try to start attaching IMO No. info to my uploads in future when it results in automatic attachment of basic ship data on Shipspotting...