Says the Shaykh: Our belief concerning the Tablet (lawh) and the Pen (qalam) is that they are two angels.1
That is to say, `We have written after the reminder, on account of Our Power, that My righteous slaves shall inherit the earth'. In this verse by dhikr is meant the lawh. And qalam is the name of that thing by the instrumentality of which the events of the time and the happenings of the world are inscribed. When God intended to acquaint the angels with some secret of His, or to send revelations to one of the prophets, the angels were commanded to read the lawh. Shaykh Saduq himself, while describing the manner in which revelation was sent down, writes that there was a lawh in front of the two eyes of Israfil. When Allah desired to send a revelation, the lawh would be brought in contact with his forehead. Thus it is apparent that lawh is not the name of an angel, nor do we find in any dictionary that lawh and qalam are two angels".
This is a very interesting refutation of the Shaykh's doctrine by his disciple, Shaykh Mufid (for whom see Rawdatu 'l-Jannat, 563). Unfortunately the original text of the Tashih on the point is not available to me. MB also mentions that such is the belief of Shaykh Saduq.
In Sunnite theology the meaning of lawh is quite different. It is of vast dimensions, of white pearl, and contains a record of everything from beginning to end (MC, 148). The Pen however was created before and has priority (ibid., 162). Two ideas emerge: (a) the Tablet as the original copy of the Revelation, and (b) as the record of the decisions of the Divine Will (El, iii. 19-20). According to Western Isma'ilis, qalam is the primal souce of the universe (FC, 21), and lawh is the most guarded Tablet (ibid., 86). The Isma'ilf influence can be seen in Ibnu'l-`Arabi. He uses qalam, lawh and `arsh for the Neo-Platonic First Intellect, Universal Soul and Universal Body, respectively (Affifi, 63, n. l; 67).