From the Jeppesen introduction section (abbreviations):
T - Terrain clearance altitude (MOCA)
From the Jeppesen introduction section (enroute chart legend):
1300T - MOCA (minimum obstruction clearance altitude)
Nothing mentioned in the approach chart legend though.
Looking at the chart again it makes sense that you have too look for it in the enroute chart legend. It is located inside the dashed box and indicates a section of the arrival and is not part of the approach section, although the IAF is within the dashed box. Maybee I have to check the introduction section again
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Edit:
Approach transition inset. Provided when route originates at an off-chart intersection designated only for approach chart use.
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