This is a Constantinopolis commemorative - the front is a personification of Constantinopolis and reads CONSTANTINOPOLIS. On the back is Constantinopolis with foot on prow (6 o'clock on your picture) and holding shield (2 o'clock) - the exergue looks like it might be readable with a good picture (5 o'clock).
Your coin is from Thessalonica, similar to the example below. There's really nothing to clean on it, the surface is flaking and you will just lose detail.
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