I only collect tapes. In this case the date in on the actual linen of the tape but you can date silver ones by hallmark obviously and styles help too. The other way is what the tape itself in made of. Silk tapes are usually pre 1880. Lots of books on the subject, the rest is experiance. Be careful of ebay, whilst there are many on there ask questions. There are a lot from 1930 onwards that are advertising items. Lots of really fun ones. I have thought about collecting them but so far am sticking to my criteria