Hello Ben, this looks like a custom lettering style and it is possible it was even created by an architect or monument shop, maybe even designed specifically for this mausoleum. An old blueprint alphabet or letter set could have been used as well, though it is rare to find them so not many have been digitized into modern fonts. The ‘ball serifs’ on certain numbers like this were often used on custom lettering styles on older memorials, usually between 1920s and 1940s, but sometimes all the way into the 1970s.
If you’d like help matching this lettering for an inscription, feel free to use the MLC Inscription Matching Service: https://www.monumentletteringcenter.com/product/cemetery-inscription-matching-service/