Hi,

First, thanks to the PVT for the amazing job. I have been working on the granted patent data for the past month or so. When looking at IPC codes, I realized some of the section codes have letters beyond A-H, which are the recognized sections. For example, I got hits for the following alternative codes [ 'Q', 'P', 'N', 'S', 'R', 'L', 'O', 'K', 'M', 'g', 'T']. Checking some of those patent IDs, I found that the patent documents do contain these section codes.

Here are some examples of patent IDs linked to IPC section codes that do not exist
O: ['4842804']
g: ['5448430']
P: ['4050266', '5346002', '5580603']
M: ['5389335', '6090647', '6267475', '6799844']
R: ['4119391', '4957574']
Q: ['4004096', '5586297', '7330824', '7689487']
L: ['4540713', '4988737', '5032249', '5234810', '5380431', '5407476', '5879940', '6562745', '7117649']
N: ['4093711', '4896202', '4967077', '6580360']
I: ['3977137', '5413850']
T: ['6367389'] S: ['4114628', '5755645', '6579545']
K: ['5014640', '6242720', '7352090'] 

Does anyone know what these might be? My first thought was that these might be old (deprecated) section codes. But I couldn't find information confirming these. Maybe typos?

I appreciate any help on this.