The two characters appear to be embossed, not punched. That they are surrounded by a frame and well-centered in the medallion suggests to me that they are not a retailer's mark or a maker's mark (or chop mark) but rather a part of the design. A quick perusal of the identified marks already posted in this section should illustrate this point.
That said, while the photos are quite clear, the two characters are not sharp enough for me to make out. If indeed they are a part of the design, they probably carry some felicitous meaning.
Sorry that I cannot be of more help than this. Someone who has seen the mark before, or who could examine it in person, might be able to give a more definite identification.