I was able to get schematics and the calibration manuals for both the 1822 and the 1855 by opening a case with LeCroy technical support. Eventually.
The first time, several years ago, I opened a case when I had only a DA1855A, and I asked for the calibration manual and the schematics. I was told the schematics were not available. But they did send me the calibration manual, which is all I really needed at the time.
When I contacted them more recently after purchasing a 1822, I requested the calibration manual for the 1822 and, like before, that was not a problem. In the course of the conversation, I requested schematics for both models because I also had to do a repair on the DA1855A. This time, they sent them to me but only after approval by their export group. I had to supply my company info for the approval process.
Perhaps they were more open now about the schematics since these units are now discontinued. Or maybe I got someone who was nice and put a little more effort into helping.
FWIW, the repair on the DA1855A was a dead PCM1702U DAC, which is the PVG generator. The PCM1702U is considered audiophile grade and sought after by that community, AND out of production, which unfortunately breeds scores of counterfeit implementations. It was difficult to find a genuine replacement.
On the enclosure, I am very certain it is a PacTec CF-225. The dimensions are right. On the units I have PacTec is printed (molded) on the inside and carries the PacTec part numbers 61815-01 on the top and 61814-01 on the bottom. These part numbers match the numbers in the CF-225 drawing.
However, I think PacTec did some customization for LeCroy, because it does not appear that the stock CF-225 has ventilation slots on the top and bottom. I did try to contact PacTec to see if they would sell this modified case, but never got a response. It shouldn't be a big problem to CNC some appropriately sized slots.
I also want to do a transplant from a rack unit to a standalone. I just don't have enough bench space for another 19" thing.
EDIT: Another notable difference from the stock CF-225 is that there is EMI shielding on most of the internal surface. I was going to try MG Chemicals 841AR-340G conductive paint.