Available from - Palatine Roses
https://palatineroses.com/rose/piro-3

Available From - Palatine Roses

https://palatineroses.com/rose/piro-3

Available From - Christianson's Nursery & Greenhouse

http://www.christiansonsnursery.com/wp-content/uploads/2019/01/Rose-List-Final-format.pdf

In "The Encyclopedia of Roses" by Robert Markley (ISBN 0-7641-5193-2) gives a little bit more information on this very mysterious rose. This is what it has to say on page 135:

Pillnizter Vitamin Rose 'Pi-Ro 3': Not all roses have the same high level vitamin C content. also, a high quantity of usable fruit flesh does not necessarily correlate with a large vitamin content. Therefore, in places such as Russia and the former East Germany, people have for many years sought strenuously to select forms of vitamin roses that combine the two factors, quantity and quality. They have found the group of Pillnizter vitamin roses, from which the selection 'Pi-Ro 3' comes very close to the desired ideal. In free-growing, decorative hedges, this shrub rose, which is produced from the native variety Rosa pendulina, displays a lush burst of flowers in spring and an abundance of hips in the fall.