Service code to get Xperia model

I'd like to check the manufacturing date of an Xperia Ray. The easy way is by looking at the sticker under the battery, but I'm trying to convey this to a potential seller, and I would prefer something that doesn't involve taking apart the phone. I've read on Yahoo answers that *#9999# should do it, but it's normally a Nokia [service code](https://en.wikipedia.org/wiki/Supplementary_service_codes) so I doubt the accuracy. I've also found *#*#4636#*#* (info) and *#*#7378423#*#* (service), which may have what I need inside of a menu. Can anyone give me a more reliable answer?