There are examples of Church sun dials in other parts of Britain and they usually follow the pattern of a semi-circle divided by radials spreading out from the gnomon at the top.
Beneath an inscription often gives credit to the Church builder.
One at Weaverthorpe in the East Riding of Yorkshire is in Latin.
Another is on St Gregory's Minster at Kirkdale, N Yorks, which is only about 40 miles from Skelton.
Some of the letters here are clearly similar to those on the Skelton fragment and the Old English, dated to the 10th Century can be read:-

MACAN NEWAN FROM GRVNDE CR[IST]E S[AN]C[TV]S GREGORIVS IN EADWARD DAGVM C[Y]N[IN]G [I]N TOSTI DAGVM EORL made------anew----from the ground for Christ and---- Saint--------Gregory-------in------- King Edward's days-------- and-----Earl Tostig's days.

The words above the dial read -
+ + IS IS DÆGES SOLMERCA + ÆT ILCVM TIDE +
----This is---the day's--sunmark------at-----each---time.

A work by Mrs Margaret Scott Gatty, 1809 - 1873 gives the following explanation of the Skelton stone:-

Part of the semicircle remains and 4 hour lines, two of which, viz., midday and 2 p.m are crossed.
Apparently the dial had been divided into twelve hour spaces.
Below these lines there are portions of 4 lines of an inscription in Old Norse or Danish, with part of a line of runes down the side.
"The runes", writes Bishop Browne, "I read as DIEBEL OK, which Mr Magnusson says is good Danish - of latish date - for 'devil and'.
He tells me that GRERA is part of the word 'to grow', and COMA is 'to come'. The words 'devil and' may well be a pious curse on creatures of that kind.
From the style of the inscription this stone appears to belong to the early part of the twelfth century.

Unless someone unearths other sections of the dial, the meaning of the inscription will remain a mystery and Skelton has a Rosetta stone.