Javier's post:
The most important towns in the Camino gives you the option to obtain the credential. May be in the Cathedral or in any albergue.
If you arrive to Madrid, you can obtain it in the Iglesia de Santiago and in the Associacion of Madrid, c/ Carretas, 13, 7º, tuesdays and thursdays 19:00 - 21:00
Buen Camino,
Javier Martin
Madrid, Spain.