In the Final Empire, coins were called "Boxings" because they had Kredik Shaw on the back, the "box" the Lord Ruler lived in. However, the Final Empire fell about 345 years before Era 2, yet they still call coins Boxings (see Shadows of Self, prologue). Have Brandon or the books talked about what these coins are like in Era 2?
The coins made by Shire Post Mint appear to be canon.
There is an AMA with Issac Stewart, who designed the coins based on Brandon's description, and is frequently in charge of canon artistic representations:
meramipopper: How difficult is it to come up with a design that pops on a coin? How do you draw something that factors in the contours that will be on a coin?
Issac Stewart: Designing for coins wasn't difficult because Brandon had already created great descriptions. The real trick was to not make it too detailed for the engraver at Shire Post! I think he did a great job bringing our intricate designs to life! Factoring the contours was something I worried about a bit, which was one of the reasons I brought Ben onto the project. I described to him what we wanted, and he painted some grayscale depth to the coins so Shire Post would have an idea of what we were envisioning.
In Shadows of Self they are described as showing a picture:
"of the Lord Mistborn on the front, standing with left his arm outspread toward the Elendel Basin. On the back, each displayed a picture of the First Central Bank, in which his family owned a large stake."
Shire Post Mint describes their own coins as:
Boxings of Elendel feature the The Lord Mistborn in the fertile Elendel valley surrounded by the words "ELENDEL", "ONE BOXING" On the reverse is the First Central Bank surrounded by the symbol for the number 1. The same weight as the historical Era 1 Boxings, these are thick solid brass coins with a satisfying reeded (ridged) edge.