The HORA 1 and SEFU hoppers were an integral part of the Kyushu coal workings. The ASO Portland cement works required coal as well as limestone workings. I think the branded wagons were for dedicated coal workings to and from the coal mines to the works. However they became mixed up with the other hoppers.
Later some had yellow bands painted meaning they were restricted to 65kmh maximum.
Also 18 of the coal hoppers were converted into cement hoppers for the ASO works. Modelled by Micor Ace.
What is unclear concerns the use of hoppers for limestone. It is possible that some were used this way but they had bottom doors while the bogie cement hoppers had side doors.
I have also found a photo with one of the empty hoppers being used to transport pit props.
The Brake van or conductor car could be found in other freight workings in Kyushu. Not very comfortable.
Try
http://shimpei.3.pro.tok2.com/0001/001_entrance/index htm
An excellent site mainly for private wagons and tank cars.
Malcolm