As far as I know Milbro never made a Scout pistol and what you have is most likely a Lincoln Jeffries Scout, especially as you say it has no trigger guard. You can see some pictures on the Vintage Airguns Gallery here: https://forum.vintageairgunsgallery....ols/#post-1272
These date from about 1922-26 and are very rare and highly collectable. When it comes to value obviously condition affects things, also if it is blued or nickelled, but in the UK a good blued example would easily fetch £300 (about $400) and a nickelled example a bit more. The Blue Book of Airguns gives similar valuations for the USA.