The symbols of Coat of Arms
Left blue means "science and truth"
Right white or silver means "loyalty"
This is also according other sources a reference to water.
General meaning of the keys is "power to lock and unlock"
This expresses power over the faithful, derived from the religious origin of the Keys of Peter, but according to an official heraldic page it means "trust, silence, helpfulness". Other sources also suggest meanings such as "authority, stewardship, security, and the power to bind and unbind".
This Coat of Arms is a mayoral power, it was possibly linked to the lower nobility.
The keys pointing down, used for the site logo which is the ancient Coat if Arms, adds nuances like "humility, readiness for use, or a lower/base position". This could be the one before mayoral rights were incorporated in the shield. There is not much known about the ancient Coat of Arms withe the keys down. We just have to accept the keys up as the only verified one.
The Crown is a sign of dignity and Authority, the Royal approval, but no longer in use
