Yes it's frequent to find cal.11 also inside the last Sifferts.

I used to find one little triangular mark behind one lug of these watches, and
two littke marks in the watches with cal.12

: Hi all: I have a technical question: The OTD Reference matrix
: indicates the 1163 Mark 6 Siffert Autavia was issued with the
: Calibre 12 movement. Could it have been possible these watches,
: indicated in this line entry, might have also been sold with the
: Calibre 11 movement? Any guidance here would be greatly
: appreciated, and thanks in advance.
: Bob in Sacramento