This and CIMRM 874 are referenced in S.Lysons, "Magna Britannia: volume 4: Cumberland", 1816, p.clxxiii, with a woodcut from which the images are taken on p.cliv, and also at British History website
No. 57. This inscription may be read "Soli invicto Sextus Severus Salvator praefectus votum solvit lubens merito." Soli invicto frequently occurson the reverses of Roman coins of the lower Empire.
No. 58 is an imperfect inscription on an altar which Mr. Horsley foundat Scaleby-Castle, but which was said to have been brought from Castlesteads: it is inscribed Deo Soli, with the addition of Mithras, the Persian appellation of this deity; of which many examples occur on altars found onthe Continent, though this we believe is the only one, which has been discovered in Britain.
From: 'Antiquities: Roman', Magna Britannia: volume 4: Cumberland (1816), pp. CXXVIII-CLXXXIX. URL: http://www.british-history.ac.uk/report.aspx?compid=50671 Date accessed: 16 August 2013.