Treat your Amiga 1200 with a new case Because time has done his odd job with help of UV light your Amiga 1200 case is most certainly yellowed to a certain level. This mild coloration for some or very hard yellowed for others is due to fire retardant chemicals located within the original cases plastic itself. These chemicals reacts to light and more precisely to UV light and one of the result for that is this yellow color your case is getting. Retr0brighting isn’t a permanent solution as the result diminish
Source: New Amiga 1200 cases – A1200.NET