E symbolizes church being the first latin letter of the word Ecclesia. In the Middle Age the Ecclesia was everything and who was outside was an outcast. The churches in which E represents a significant percentage of the total of symbols belong to the orbit linked to Cluny.
San Martín de Frómista (Palencia), San Pedro de las Dueñas (León), Catedral de San Pedro de Jaca, San Bartolomé de Ucero (Soria).
Read more in The stonemason’s signs in the Romanesque churches in Spain.