Hi Colin,
take your time to make good photos in case you want help, so we can see details.
The above additional photos do not show much. There seems to be a HAMON, but no details like NIE, NIOI or HADA are visible.
Again, for good contrast images, use a plain dark background and a dark room (which will avoid reflections), preferably with a single spotlight, and show the whole blade tip-uwards, without TSUBA, SEPPA, or HABAKI.
Your sword looks like an authentic civilian Japanese blade, mounted in a military SAYA (= leather covered scabbard). HABAKI looks nice, TSUBA cannot be seen properly. Is there something (a date?) chiselled on the URA (other side) of the NAKAGO? The photo does not allow to see it clearly.
Private swords (not always "family heirlooms") are seen being adapted for combat use in WWII with a military SAYA and, sometimes, other military mounting parts. The original WWII blades were mostly in the 630 mm range, but other dimensions occured as well. WAKIZASHI sizes are less common.