top trigger question

Hello all,
My first post, after an introduction, pardon any terminology gaffs.
I've seen (in the flesh) a crossbow with a short trigger mounted on the top side of the tiller, but can't seem to find any info anywhere. It appears to be a simple lever, push the pad down and the opposite end pushes the string up off its ledge(?).
Something like this, pardon the bad sketch.

Is there any historical basis for this? Any drawbacks? It seems fundamentally simple, but...

Thanks,
Frode

I know there are historical examples of that kind of lock. I want to say that they are more common on early oriental crossbows.

The issues arise when dealing stronger bows. As the draw weight goes up it take more and more force to push the bow string up over the ridge. So to get more leverage the lever is going to get so long that it becomes unwieldy or the lever simply is not strong enough and bends instead of lifting the string. So for a simple light weight crossbow. Say a target or small game bow it would be fine.

I think it would be neat to see a bow with that sort of mechanism.

That is the type of release on the crossbow I tried out last week. It was built by a gentleman in our local SCA group and had a lever on top you pressed down with your thumb. The lever pivoted upwards (very close to the notch) pushing the string up until it cleared the notch and sent the bolt down range. It was very tough to push down with my thumb, and almost too tough for my wife to do. His crossbow was approximately 60 pounds weight with a 10 inch draw. Your sketch is pretty close except the pivot point is much closer to the end where the string will be, say 3/4 or 7/8 of the way down the length of the lever. He got the design from someone else online, I'm not sure where.

The top-trigger (sometimes called teeter-totter trigger) is very common on SCA combat bows. It works pretty well for lightweight bows if you plan for sufficient leverage from a stiff trigger. The only downside I see for mounting the lever on top would come from having the release in the middle of your sight picture. Of course if you're shooting big fudgy SCA combat bolts, that's no real problem. You have to elevate a bit to hit your target anyhow. The well-known 'Skane' crossbow (from Josef Alm's "Survey of European Crossbows) uses a bottom-mounted lever that can be made much longer, without interfering with sighting.
The only printed source I have seen which shows a teeter-totter trigger is one of the the Osprey Men at Arms series. These books are usually fairly well researched, but certainly not infallible. Otherwise, All the documentable notch releases I know of (both asian and European) put the trigger or lever on the bottom. So the teeter-totter is simple... I have no doubt somebody in antiquity tried it, but the Skane bow is quite well documented, and is a proven performer. I recommend you try it instead. Geezer

I can´t resist to google it....
Looks like the beginning of the crossbows, as simple as possible..

Thanks everyone! Sorry for the delay checking back in (life). I think the bow I saw was probably a light target bow that could be modified for SCA combat bolts. Aluminum prod, too, I remember that.
I've been asked to put together a target cross bow tiller with a simple trigger mechanism. The requester has had issues in the past with roller nut triggers (binding, wearing, etc.) and hoped to perhaps avoid that in future. Requester will be providing a prod, so I don't know quite how I'll be proceeding yet. It'll probably be in the 60 pound range.
I'm of two minds, certainly something like the skane bow, or the teeter totter trigger look easier to make, on the other hand setting up to do a proper roller nut would be time well spent. I guess I'll know more when I learn what the weight and reaw of the prod are going to be.
Thanks again!
Frode