Most plans are part of the RHP series, with two important exceptions:
- the first is the sasine plans, which were recorded as preservation writs from 1868 onwards (our reference RD16). From 1925 duplicate plans could be also recorded along with the sasines or, from 1934, recorded with the deeds themselves.
- the other is the series of Ordnance Survey maps marked up in connection with a survey by the Inland Revenue to determine the value of all land in the United Kingdom, 1909-1915. They provide the key to the Inland Revenue field books (our reference IRS). Our guide to Inland Revenue Survey Maps and Field Books provides further details.
