Astoria is a brand historically connected with Montblanc; Astoria nibs are original and models from the 1920s and 1930s do exist. A safe assessment is only possible from clear pictures of the section, feed and blind cap. In the concrete case, an atypical section, unusual imprint and atypical blind cap argue against Montblanc/Astoria; the piece could rather originate from Osmia. Often no-name pens with Astoria nibs and subsequent engravings are passed off as valuable pieces. Damage such as hairline cracks, chips and discolouration should also be checked. With uncertainty and a price in the four-figure range, the purchase is advised against.
Related pages on fountainpen.de:
• Astoria — brand overview (fountainpen.de): https://www.fountainpen.de/astoria-en.htm