Chinese style bowdrill

I managed to snap some photos of two bowdrills that Gao Yisheng brought into the woodshop before his departure. The bowdrills have left with him but my curiosity remains. They function identically yet while one is clearly a smartly fashioned homemade model, the other shows signs that it was manufactured.

side by side

Besides having a surface finish, the bowdrill on the right appears to be manufactured (yet I could find no brand markings) because of the larger alloy ferrule that accepts drill bits or bit pads and the ball bearings set inside chrome plated races. (The ferrule on the handmade version was nearly rusted through.) In spite of this, the bowdrill is rather crudely made. There is a bit of loss where, it seems, a lathe operator gouged out some short grain but it was still deemed acceptable. It's the putative handmade tool that has this detail on the handle that distinguishes it as more refined and adapted by a user for a user's comfort.

The more elegant handle of the two

the ferrules

By contrast the other bowdrill handle is a straight dowel with a wider section for a handle that is also warped along its length. Whether intentionally or not is unknown. I don't know anything of their provenance nor was I able to use them. They arrived as is and without and attachments. The cords were similarly rotten and would have required restringing before attempting to test them.

Planing stop, croche, and bowdrill

I managed to photograph a similar tool while on a woodcraft tour of TianTaiShan.

unguarded combination machine

Bespoke furnituremaker

I spotted this one on the workbench of a furnituremaker. He seemed to use it exclusively for drilling the alignment holes when gluing edges of wide boards. Opposite the work bench, he used a jointer with a drill chuck attached to the cutterhead spindle as a horizontal borer. The main source of lighting came through the front entryway so I failed to get a good photograph of the drill bit. Describing it in words is sufficient. An iron nail had been pounded flat and then sharpened to a point with two cutting edges. This was then driven into the end grain of a block of wood (pad), which was forced into the bowdrill. This was not a refined tool. I could see that replacing the pads had damaged the opening, probably with a screwdriver. It might have been made at one time to accept better crafted bits and pads. As it was, it served the joiner to drill the holes for bamboo dowels when making round tabletops from boards. At least in this form, this bowdrill is in no way an accurate tool and is very limited to small size holes. It is comparable to putting a finishing nail into a drill chuck. It does a task but in a very limited application.
I want to believe, at least, that at some time, drill bits and pads were made specifically for this tool, either for manufactured bowdrills or to be used in conjunction with homemade versions. I've never seen these tools used on a construction site and I have no idea whether any craftsmen prefer them over the more readily available cordless drills on the market today. It might simply be another example of the conservative impulse in so many aspects of Han Chinese culture. It nevertheless might have some advantages that have yet to be identified.
Short of finding a set of bits for this tool, there exists a possibility that evidence exists in printed form, possibly in advertisements or in tool catalogues. I am still looking for a cooperative scholar with connections in one of the state or university archives.  
If any reader has a suggestion where to pursue this line of inquiry, or wants to add anything to the discussion, please reach me through the comments.