This post serves no purpose other than to have a list of who owned what lots on Square 507. If you are interested in who lived there, check out the Square 507 (bounded by NJ, RI, FL, 4th and R Sts NW, with Richardson Place in the middle) page at TruxtonCircle.org.
This is from the National Archives Catalog for RG 351 entry P1, General Assessment Washington City, 1933-1934, File NAID 143492761.
If you want to match “most” of the lots with whats above, go to DC Property Quest.