I believe mTech is the house brand of the DRO Store, appears to be an American outfit.
Website is http://www.thedrostore.com . Might be worth contacting them to see if they have download on site. Most suppliers do haver a documentation download link but this one doesn’t appear to have one. Design and layout about 10 years behind the times!
Almost certainly a bog standard Far East DRO box so odds are the operation is generic. Instructions for any other breed with same front panel layout may well work just fine.
Clive