you was not alone in your thinkingI had a good look around the web and only turned up screw thread for Astra M8. I know this sounds a bit daft, but are you sure you didn't get query like "Is it an SRi M8?"
Because I'm a grammar nerd, I would put in a comma "Is it an Sri, M8?" and then slap myself for using "M8" instead of "mate" which is what M8 means to a texter from the mid-2000s. Could be just being friendly with the enquiry.