The company is called "BetStone Ltd." out of Ireland. AFAIK all their modern games are all run and controlled on a master server through secure VPN connections, so unfortunately I don't think you won't be able to run the machine independently... so you may have to try and source your own software/game/whatever you ultimately decide to use the cabinet for.
as for opening it, if you don't have keys... get out the grinder and drill and start cutting/drilling the locks off.
to open the top, you typically have to unlock and remove/open the user control panel and then either have another lock under there or other such lever under there that releases the top monitor portion for service.
you can try emailing info@betstone.com and see if you can weasel some info out of them... typically casino machine manufacturing companies don't release manuals for their machines (for obvious reasons) and people (resellers) often have to make their own, but it's always worth a try if it's an older machine they no longer support.
I often have to socialize my way into restricted info from companies. Business like this, being that they deal with real big money, are a little weird so don't come right out asking for everything, just ease into whatever info you can get. you basically want to earn a friendship with someone on the inside to get what you want.
Just call or email and just politely tell them you bought this cabinet and ask for some basic information about the cabinet, how it opens, tell them you got all the keys for it and are planning to make your personal game in it or something. once you are a few innocent sounding questions on the phone/a couple emails deep with whoever you are talking to, ask if they have any manuals or the like.
they will be much more forthcoming with info if they know you are 1 - not trying to reverse engineer their software or something. (making them or their clients lose money) 2 - not trying to scam people with their name on their machine. (making them look bad)
good luck! I'd be interested in seeing what you might do with this besides a VLT.