I was taking a look at the knockoff grips on eBay and it seems like there are multiple sellers but there are two types of grips.
Take a look at these details on the front:
1 - Take a look at the connector things, on Grip type 1 it is plastic unlike the genuine grip. On Grip type 2 it is metal just like the genuine grip.
2 - Take a look at the curve and where the grip ends. Grip type 1 is less curvy and the grip is off. Grip type 2 is more curvy like the genuine Pentax grip and the grip extends to the correct spot like the genuine grip.
3 - Take a look at this little thing, on Grip type 1, it's just a little thing sticking out. On Grip type 2, it looks closer to the genuine grip. On the genuine grip, there is a circle cushion popping out of this thing while on Grip type 2, it doesn't have cushion.
4 - Take a look at the black screws around the tripod-mount. On grip type 1, it has only two screws. On grip type 2, it has 6 screws which is the same amount as the genuine.
Conclusion -
The only difference I can tell between Grip 2 and genuine is that genuine has a different label saying PENTAX on it and with cushion. While on Grip type 2, it doesn't have the genuine Pentax label and it has no cushions.
GRIP TYPE 1 FRONT
GRIP TYPE 2 FRONT
GENUINE FRONT
Take a look at these details on the back:
1 - On grip type 1, the grip once again gets cut off. On grip 2 type, the grip extends through the curve line just like the genuine.
3 - Look at where the screws are placed, it's different on both grips. Also look at how Grip type 1 has a hole that's popping out. On Grip type 2 however, the hole is recessed. On the Genuine grip, there are cushions sticking out of these holes, however the Grip type 2 it has no cushion.
GRIP TYPE 1 BACK
GRIP TYPE 2 BACK
GENUINE BACK
Here is the group selling Grip type 2, closer to genuine grips.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280439064218&ssPageName=S...#ht_3013wt_859 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220527760188&ssPageName=S...#ht_3000wt_890
Here is the group selling lesser to genuine grips, Grip type 1.
http://cgi.ebay.com/Battery-Grip-for-Pentax-K7-D-BG4-D-Li90-Battery-B1Y_W0QQ...ht_2641wt_1084 http://cgi.ebay.com/Pro-Battery-Grip-B1Y-for-Pentax-K7-As-D-BG4-1x-D-Li90_W0...ht_2583wt_1084
EDIT: I also forgot to mention that the contacts on Grip type 1 is large and fat. While on the Grip type 2 is also thin like the genuine grip. This is pretty scary because it looks all the same except it's missing cushion and it has a different label.