Jelly is probably considered old fashioned now and not sophisticated for children or adults to consume. I remember it with fondness from childhood and my own children's childhood as a treat. Jelly and its more elegant, but less tasty cousin, blancmange. Either one wasn't served in just any old bowl, it had to be in a jelly mould which came in all sizes and shapes. I recall a glass rabbit mould which I loved but it must have gotten broken somewhere in the passing of time.
I found this old pressed glass mould in a cupboard when clearing my mother's house. I remember it being my grandmother's, who lived with us, and it held many a sweet treat. In the 60s jellied salads became the rage. They weren't healthy but got vegetables into reluctant children. I recall one made with pineapple and grated carrot in lemon jelly and another with lime jelly and green peas. I know...yuck right? See here for some "interesting" salads that were made with jelly.
The bubble topped jelly mould was common and made anywhere from the 1930s to the 1960s. Seeing the contents layered through the glass made the eating more interesting perhaps.
Now as for drawing glass, its one of those perceived difficulties. Its all about light and shade and picking out the specific areas of each as well as those subtle variances of mid tone with bright shots of white highlights that made it work. Observation is key for glass, but very achievable if you take your time. This is a quick sketch in my Moleskine with a few wonky angles as I didn't measure, but I see it appearing as a larger charcoal piece in the future.
