Sometimes they write “handmade”, but that's just marketing. What are the signs that tell you what is really handmade?

I have a little bit of different premium products from leather https://leatherav.com/ (who is interested took most of the accessories from A&V), and with confidence I can say that the handmade work is immediately visible by the seams - they are not so perfectly even, but at the same time much more aesthetic, durable and neat.