Learning Hebrew

Ordinary Chaf        Final Chaf

Ordinary Mem       Final Mem

Ordinary Nun         Final Nun

Ordinary feh           Final feh

Ordinary tzaddi[k]       Final  tzaddi[k]

• from Chabad.org site's explanation of the last 5 letters - in simple summary, the alternate form of the last 5 letters were communicated to prophets for the sake of prophecy.  see, here:  Chabad.org

Ironically,  however,  not all Rabbis, students or even leaders may know and/or remember all the fairly complex info, if were to be asked, 'on the spot' - for example when in a 'special moments' study session in L.A. - when studying the Gateway of Trust (Bitachon) - asked what letter equals the number 600, of which the response is, none of them!  and emphatically stated, there's a letter that equals 600! ...looked at the simple chart online and thought was incorrect, good thing there were additional letters and numbers for different tasks...