Please could you tell me what my cymbals say?The answer is quite simple. It is the Avalokiteśvara mantra written in a Tibetan script called dbu-can (pronounced uchen) - the main formal script they use for texts and printing. The extra symbol is a paragraph marker, known as a 'shed' in Tibetan. It's more often a simple vertical stroke, but sometimes a colon-like thing as you have here.
I've been taking these cymbals into prison for over 15 years, to ding meditation stages. Occasionally, someone asks me what the symbols mean. I confidently reply that it is the Avalokiteshvara mantra.
Only, last week a bright spark asked if it says "om mani padme hum" how come there are seven symbols rather than six?
oṃ ma ṇi pad me hūṃ :
I've added the letters onto your image so you can see which is which. While we're on the subject there is no word break in maṇipadme - it is a single compound word meaning, most likely "in the jewelled lotus" (but clearly not "the jewel in the lotus" as Sanskrit grammar does not allow this meaning, despite it's popularity). I've written about this on my blog post "The Meaning of oṃ maṇipadme hūṃ".
Note the Tibetans write "pa dme" as "pad me" because it looks more Tibetan. In the image below the top line is what is on your bells, and the bottom line is the proper Sanskrit, but still using the same script.
One also sees the mantra on these kinds of bells written in the Lantsa script (below).
My compliments to the bright spark who spotted that there were seven symbols!