Thank you guys for your help.
Yes, it does appear to be an RG548. The seller got it second hand and I guess he never bothered about what model it was. I just wasn't familiar at all with this model. In fact, I didn't know there were natural finish RG4xx or RG5xx guitars... and I was thinking it was probably a stripped/refinished guitar.
I have decided to go ahead, and soon that baby should be resting in my arms. On my strap anyway... and I am not sure "resting" will be exactly the right word to use.
This will be my first Ibanez. Who knows, maybe I'll catch the bug and end up with a Jem sometime