Sample Sales Packs we made for Open for Vintage involving quite a lot of research and product testing to understand and develop methods of printing on black card (and all types of paper), gold foiling, wax sealing etc. Was a lot of fun and we ended up buying a good bit of equipment along the way for future use. 
Needless to say the clients were over the moon with these and they'll be going to full scal production soon. 
"Open for Vintage" logo printed in black on black card. The envelope is sealed with a gikd wax seal
OFV logo is gold foiled onto the letter and is revealed when the envelope is opened
Each stage of costomer experience is thought of. From the texture of the paper to the directions of the fold and branding placement.
The full logo is then gold foiled above the sales pitch as an elegant brand recognition.