The year is 1900
You are a general store.
You need to advertise widely to promote your store.
You have an idea.
You will make up a small booklet of items for sale,
and put them in envelopes.
The envelopes will be prepaid, and sold at half price.
That way when your customers use the envelopes
to send to their friends, the booklet goes with it

You get huge wide distribution of your booklets
at half price!
The purchaser subsidises your distribution.
How was it done
