Digital BW, The Print

We would like to include in the same limited edition, the same print
done with two different techniques. For example, in an edition of 45,
we would like to include 35 Carbon-Gelatin prints and 10 Piezography
prints. The paper and image size will be the same, but the two papers
would be different. I surfed the internet and found nothing. We would
like suggestions and recommendations for a numbering scheme.

Thanks.
  Daniela