It is a white cardboard with bevelled edges placed between the frame and the photograph. The mat has a double function:
Munich, Germany, November 9, 1923. The public square in Munich which was the center of the Bavarian Royalist revolt last night which appears to have failed.See all photos from Bridgeman Images
Bridgeman Images - Underwood Archives/UIG / Bridgeman Images
Your photograph is printed on a high quality satin photo paper in 250g thickness. Thanks to our high-performance printing systems and a sharpness of up to 1440 dpi, we guarantee you a product worthy of the greatest art galleries. If, despite our expertise and precautions, you notice something wrong with your product, we will send you a new photograph at our expense.