  The radio-loud quasar CTD 135 (2234+282, J2236+2828) has been proposed as a
candidate compact symmetric object (CSO), based on its symmetric radio
structure revealed by multi-frequency very long baseline interferometry (VLBI)
imaging observations on milliarcsec angular scales. CSOs are known as young
jetted active galactic nuclei (AGN) whose relativistic plasma jets are
misaligned with respect to the line of sight. The peculiarity of CTD 135 as a
CSO candidate was its detection in gamma-rays, while the vast majority of known
gamma-ray emitting AGN are blazars with jets pointing close to our viewing
direction. Since only a handful of CSOs are known as gamma-ray sources, the
unambiguous identification of a single candidate is important for studying this
rare class of objects. By collecting and interpreting observational data from
the recent literature, we revisit the classification of CTD 135. We present
evidence that the object, based on its flat-spectrum radio core with high
brightness temperature, variability at multiple wavebands, and infrared colours
should be classified as a blazar rather than a CSO
