I used to take a packed lunch to school, and I remember that Mum used to give me a drink of orange squash in one of those old Thermos vacuum flasks. For some reason these were quite often made with a tartan design printed on them, but I’m pretty sure mine was a solid colour. These flasks kept drinks hot or cold by virtue of the vacuum between the outer flask shell and the inner glass chamber, which had a reflective coating. Unfortunately this made the flasks easy to break, and indeed one day my flask innards were smashed after dropping my school bag.
After going through several replacement plastic bottles which all leaked, we chanced upon a new invention called the Roughneck Flask, whilst we were on a family holiday. It was still made by the Thermos company, but was made entirely out of plastic, and very robust plastic at that. In fact, the weak point in these flasks was the cup that screwed on the top, something which had normally been quite reliable in the old Thermos design.
I have no idea why it was called the Roughneck Flask. My best guess is that you could be quite rough with it, and that it had a neck from which to pour your drink. The design was aimed squarely at kids and it excelled. It was square and quite short, which meant it fit easily in your school bag, and obviously its unbreakable nature was very important. I think it even had the word unbreakable printed on the side.
The other thing that distinguished it as a child friendly product was the picture printed on the side. Most of these pictures were of well known TV and film characters. Mine had Yoda from Star Wars on, whilst my sister had one with Kermit the Frog on.
Thermos went on to produce lunch boxes to go with the flask too. You could buy a lunchbox with a hinged lid that had a picture stamped on it, and a little carrying handle. Inside would be a Roughneck Flask to match the box lid, which was kept in place by a couple of plastic flanges that stopped your sandwiches and crisps from getting smashed to bits.