How to calibrate speed on HiFi cassette deck?

[Dragon]

You need a test tape, which you'd have to buy from a pro audio repair supply shop (MCM Electronics might have these), since if you attempt to record your own you won't know if the recording deck is on spec or not...of course, if you have a tone generator and frequency counter you can check any deck and then perhaps make your own.

You may assume I don't have a professional deck available.

Also, some places quote 1-7/8 ips, some
quote 48mm/sec (which is slightly higher!)..?