Buffet Clarinet identification .Model designation

n�1 indicates polycylindrical bore
Am�rique appears to be the designation for an R13 made for American market

It looks like that if there are no other codes, it is assumed to be a R13

Decoding the letter and number sequence

For a sequence such as BCxxyy(c)-d-e ……………

BC = Buffet Crampon

xx
This specifies the key, with
11 = Bb (old code, SiB=Bb)
12 = A (old code, La=A)
15 = Eb (old code, MiB=Eb)
17 = F

yy
This specifies the model, with
02 = E13
12 = RC
31 = R13
83 = Prestige RC Bass to Eb
93 = Prestige RC Bass to low C
23 = Basset

c
Optional code, meaning
G = greenline
L = Left hand Eb lever

d
Specifies key plating, where
02 = silver
05 = nickle

e
Specifies pitch
0 = 440
2 = 442
4 = 444

So

BC1131(L)-02-0 equals a Bb (11) R13 (31) with a LH Eb lever (L) with silver plated keys (02) tuned to 440 (0)

Information attributed to Jack Kissinger and Francois Kloc

Edit:
For completeness, the website to check the serial number of your instrument (for E13 and professional models) is

http://www.buffet-crampon.com/en