E11c was a variant of E11 that ran on separate schedules. It was an alternative null message format, that included an additional, middle 4-digit segment in the ID. First heard on 22 July 2010^[1], last heard on 18 April 2013^[2].

Format:

The 4-figure group was not random. It usually ended in "00", and contained "0", "1" and/or "2".

Prior to 1 May 2012^[3], the middle segment was a 3-figure group that consisted of one digit repeated thrice (no groups other than "555", were noted though):

References

1. ENIGMA 2000 Newsletter #60, p. 2 (September 2010) [accessed August 29th, 2014]
2. ENIGMA 2000 Newsletter #76, p. 59 (May 2013) [accessed August 29th, 2014]
3. ENIGMA 2000 Newsletter #71, p. 40 (July 2012) [accessed August 29th, 2014]