It's the shape of a marmalade dish (without the ruffle around the middle) but it does look as if it was made to fit into a holder.
In Bohemian glass, citron is a very pale yellow, but I don't know whether or not it was used as the name for other colours in other places. 
Thank you for the additional information. I've just googled citron and going off Kralik citron, it does look pretty similar. However, I'm definitely no professional *lol*. I shall go snooping at marmalade dishes now, thank you!
