The flying-underwater thing has never made sense to me.  Water, like air, is a fluid so the wings of an intact airplane sinking nose-first, so the theory goes, should generate "lift" and the aircraft could "glide" for a considerable distance from where it sank before reaching the bottom. 
Let's try an experiment.  Fire up your airplane and climb to whatever altitude suits you.  Now shut off the engine, take your hands and feet off the controls, and don't touch the trim.  Nothing good will happen.   Flying machines remain under control only through human guidance. The Wrights figured that out a long time ago.

Wondering if anyone has done a scale model test of a properly weighted Electra model to see if it would "float and fly" vs. sink. Given that Ballard didn't find anything near the shore the other hypothesis could be that it's much further off the shore if it "flew".
Don...

Ric, I think this hypothesis is sound. We must persevere.

'Recuit' treatment is justified for a laminated ('écrouissage'), bent and stamped part ( that needs to retain its tear strength.

For the moment, I can't go any further on the subject. I'll try to find more studies on French special steels around 1930.

If I see anything else, I'll let you know. We'll be in touch.  

As for the high silicon content, isn't it possible that the artifact had been contaminated by the sand at the bottom of the pond, which has aggregated with it?  You mentioned that the scan was surface scan only.

I had the same thought, but apparently not.  We have a 1975 breakdown (see below) of the elements in Gull Pond (referred to by its topographic map name Goose Pond).

Interestingly, there is no naturally-occurring:
• Silicon
• Vanadium
• Titanium
• Tin
• Phosphorpus

Alll of which were detected in the XRF scans of the artifact.  The titanium (like the cobalt and lead) is probably from the paint. The silicon and vanadium are apparently part of the alloy. The little bit of copper could be from a tiny pocket of sediment. There shouldn't be any phosphorous in alloyed steel so it's probably an impurity.  Ditto for the trace of tin.

If I’m right, the base metal is steel alloyed with manganese, molybdenum, chromium, silicon, zinc, and vanadium.  That’s a complex, very high-quality “special steel’”.

I couldn't find any mention of L2R among French forges in 1918... But if Levasseur uses it in 1929, it's because it's an established standard, and probably a widespread one.

Agreed.

The 'R' reference could be the metal treatment. Perhaps a reference to the French term 'recuit' which is a heat-tratment of the laminated steel (beteween 500 and 800 °C) to restore his original mécanical properties.

That would make sense.

Ric, a few thoughts.

As for the high silicon content, isn't it possible that the artifact had been contaminated by the sand at the bottom of the pond, which has aggregated with it?  You mentioned that the scan was surface scan only.

I couldn't find any mention of L2R among French forges in 1918... But if Levasseur uses it in 1929, it's because it's an established standard, and probably a widespread one. I will see if i could track any classification around 1930.

The 'R' reference could be the metal treatment. Perhaps a reference to the French term 'recuit' which is a heat-tratment of the laminated steel (beteween 500 and 800 °C) to restore his original mécanical properties.

By the way, i found a source reporting that Le Creusot (Schneider) had won a contract to build parts for the Lorraine 400 hp engine. It is not specified what type, however. Il could be the V12 e 12Db around 1918-1919. So it is likely that Lorraine had established good working trends with Schneider.

But i need more sourcing for all of these.

 

Ric, really bravo, I think you're on to something here... Investigating the composition of the alloy is a good idea. Rather than finding the part, let's find the material!

The L2 standard is, nowodays, American.  In France, we refer to 80CRV2 (Afnor).

Nevertheless, The L standard was already known in France in 1920, and is referred to as “Houille Blanche”. At the time, it was a hard carbon steel alloyed with nickel-chromium to prevent wear, oxidation and deformation. For the time, a standard of tooling. Quite a different acier spécial compared to L2 and the artifact.

Interestingly, the Levasseur spare parts catalog dates from 1929. It's a direct source that categorizes the steel in question according to standards for which an international standardization effort may have been made between 1920 and 1929.

Whatever, it is, possibly, a first direct step and link between the artifact and a first sourced docuement from Levasseur.

Page 35 of the PL4 Parts Manual shows the "Feuilles Metaliques" (sheet metals) used.  There are two steels listed, "Sheet steel No. 12" and "Alloyed sheet L2R".

The latter is presumably the "special steel" referred to in the part descriptions.  I can't find a definition for L2R steel but L2 steel is described on
https://en.wikipedia.org/wiki/Low-alloy_special_purpose_steel
In the attached screen shot, I've compared the element averages found in the XRF scans with the corresponding allowable ranges for L2 steel.
Most of the artifact element averages (shown in green) meet L2 specs. Only the averages for phosphorous and silicon (shown in red) fall outside the limits – both are too high.  Phosphorus showed up in only one scan, so that anomaly can probably be dismissed.  Silicon was detected in 4 scans, so there was probably really some silicon in the alloy.  Our artifact appears to be L2 steel with silicon added.  Maybe that's what the R stands for.

At the very least, our artifact appears to be made of steel very similar to steel known to be used in the PL4.

However, the presence of a preheater is only assumption i am afraid.

True – but it's the only thing we've found so far that seems to really fit the artifact, including a film of oil on the interior surface.
 

If there is an oil heater, it should be lower than the tank at the rear of the engine, not far from the pump.

I've reviewed the PL4 parts catalog: there are feeders for water (double feeder) but not for oil.

The PL8 is indeed the contemporary of the PL7 in its first version, so much so that Levasseur himself had insisted that Nungesser adopt the Hispano Suiza instead of the Lorraine.

Certainly, for a trip in fairly low-temperature conditions, this device would have been useful. 

Several accounts state that the engine was tested and preheated at around 4am.

According to the testimonies, Nungesser left the engine running for between 2 and 5 minutes, probably more like 2 minutes. The take-off time is reported as 5:18 a.m., sometimes 5:21 a.m.

However, the presence of a preheater is only assumption i am afraid.

LTM

Leafing through my books, I found this image of an oil feeder adapted to the PL7 (the cylindrical item)

I know that this aircraft had a Hispano-Suiza very different from the Lorraine. This oil feeder was intended to allow the oil to be preheated an immediatly in  use for a quicker and safer throttle-up.

We know that it's likely that the PL8 version 1 had an oil preheating system. Could it be that Levasseur adopted the same system as for its contemporary PL7? Do you have any assembly diagrams? (I do not possess any).

No assembly diagrams, but the pictured oil preheater could be the right size to be our cylindrical artifact and the cap on the filler neck could also be right for our disk artifact.  Did the PL8 have such a device? If so, where would it be located?  I don't know how the preheater worked, but the detailed press accounts of the takeoff on May 8 say the engine was started at 5:15am and they started the takeoff run at 5:18am. Three minutes is not long enough to warm the oil.