SMD Diode Packages

Pic of dc2012x14dc2012x14
Diode Chip 2.0mm Long, 1.2mm Wide, 1.4mm High
If there is a polarity mark the mark goes to the left.
Pic of df3414df3414
Diode Melf 3.4mm Long, 1.4mm Round
Since m is used to indicate a molded package the last letter of the word melf f, is used in all melf names.
Pic of dm4327x22dm4327x22
Diode Molded 4.3mm Long, 2.7mm Wide, 2.2mm High
Consistent with the Zentroid SMD Naming Convention the length is taken from pin end point to pin end point. This gives the programmer an excellent start value for centering or testing operations.

I have found a rather good resource for diode information at Diodes in particular can have a large variety of packages.