well, buy it from a reputable seller is the only option. you cannot examine the stock before hitting that buy button after all , when shopping online. And on that, you will not find the 616 standard size in blister pack of 10 since it was never packaged that way. The Blister pack of 10 is used for the small sized 616 , 616-2, and 6161A ( all are engineering vise the same, different color and trim only ). The Doctor sub brand is just Hero's specific brand targeted towards academic / school supply market. Read, certainly does not mean quality either. the best quality 616 is the very rare gold nibbed version ( long out of production ) and the export version ( usually those that are packaged individually in their own box ).
Reputation comes with good transactioning not necessarily from opinion about pens. We all understand that pen-reviewing is a subjective process and has everything to do with the level of expectations of the buyer. For example, if I see someone with a few hundred satisfied buyers who keep on saying "good pens, good seller, happy with what I bought" does not really answer the questions that are being posed here.
Also, what do you do when the so-called export options, sold in their individual boxes, actually have boxes that say "iridium tipped nib" and has no reference to the nib being of any caliber of goldness? How does that set it apart form what is being sold in bulk and much cheaper?
And how/why would you trust anyone who uses the word "genuine", if that means anything anymore", when the word is being thrown all over the place in listing titles and there is no measure of testing the genuinity of it?
And what do we make of reputable sellers who sell the "genuine" pens for what we consider to be reasonable prices for the "rare export" items (say, £5 a piece, as opposed to £1 a piece), when the same seller sells for example Jinhao's £1 pens for £7? Is that also a better make of the same pen from a better factory/batch?