i got on bay industar-69 28mm F2.8 for 30 bucks from ukraine. and old lens for old russion camera from early 70’s. with the leic m39 adapter it makes pretty small package together with nex5. there old lenses and heavly used. same of the lense can have lot vignette or scratches etc. same people buying 3-4 lense to get a good one. i just gamble and order the next best one. my lens was medium-heavy used its have same vignette wide open. before you use on nex you adjust the bolt/stopper inside the lens. its quite easy, you just need smal screwdriver. mike kobal have how-to video on his blog.
the lens is not the sharpest wide but its still ok. it gets better at 5.6. its not sharper lens but its has nice look, specially in black and white. overall it makes a nice street shooter lens if you not wanna get supersharp images for huge prints. the best thing is: its so small. because this smal pancake size the apture control is on the front side of the lens, which is little annoying.
the lens is metal build and feels soild. the focus ring need many turns if focus from far to close. with the removed bolts (show in the video) i can focus close as 20cm.
*edit
i’ve used the TEKTON 2987 Precision Screwdriver Set. a another thing, i found out, the lens can not focus to infinity. because of the distance to nex sensor. you need filing down the focus ring. –> the focusring can turn deeper into lens body and allows a infifinty focus.
check out the images. shoot in 2.8 and 5.6
Heribert Raab 
Can you please mention the screwdriver type that’s used? Thanks in advance.
i’ve used a TEKTON 2987 Precision Screwdriver Set
Thanks so much for the quick reply. I’ll be getting this soon :)