There is a series of highly collectible dual branded bars that are SILEC and Engelhard. I've only ever seen one. SILEC became Siltech. They've been around since forever.
Modern Siltech bars had a stamp with a logo inside an oval shape up until recently.
The new logo, which is kind of art deco has been spotted on 1kg loaf bars, 5kg loaf bars and 1oz gold ingots.
Goldstackers has the 5kg in stock as far as I'm aware, so hit em up.