How to get a Diameter Symbol
The diameter symbol is present in Microstation Engineering font (number 3) resource file (font.rsc). You can view Microstation symbols in FontEdit (keyin: mdl load fontedit). Load the font.rsc file and set to Engineering font (3). You can view the diameter symbol and see keystroke 201.
You can place a diameter symbol by using the WYSIWYG editor or by using Dialog Box as Text Editor. When using Dialog Box as Text editor, type \201 to get the diameter symbol.