There are two types of e-certs issued by United. Both have "serial numbers" with one starting with "016" and one staring with "TCVA". TCVA e-certs also have a PIN associated with it and are generally issued as bump certificates or sent via customer relations after you contact them for some sort of dis-service on a flight. 016 e-certs are/were* issued when you are given a form from a f/a on-board a flight or are sent an e-mail from customer service regarding some sort of dis-service on your flight. Both serve the same purpose in reducing the fare cost but TCVA e-certs take off from the ticket cost but the full price of the ticket is still included as to what was actually paid vs a 016 e-cert reduces the ticket cost as a discount. The net out of pocket will be the same but with PQD's now being included in premier qualifications, one wants the full price of the ticket included vs the discounted amount in order to get maximum PQD's

Example:
TCVA
$250 base fare + $25 in taxes = $275 total and using a $250 TCVA e-cert, the net out of pocket is $25 but the ticket cost is $250 and $250 counts towards PQD's

016 016
$250 base fare + $25 in taxes = $275 total and using a $250 016 e-cert, the net is also $25 but the ticket cost is reduced by the $250 to zero and thus zero PQD's on this ticket

*hence my question about if the 016 e-certs are still being issued