The clickykeyboards site states that they one they sold was a one-of-a-kind. To better document both boards, I've copied the data here:
part# 1391401
serial# 3702060
date 13-DEC-88 (17 years old)
IBM logo black logo on white background
cable removable, coiled cable, ps/2 connector (NEW, extra long cable in original package)
key caps removable (two piece, key stem + key cap)
key switches clicky = buckling spring
part# 1391401
fru# 1392090
serial# 7734787 (id#)
date 25-JAN-1993
plt# L1-CW Model M
IBM logo blue logo on beige background
cable removable, coiled cable, ps/2 connector with built-in ferrite on ps2-end
key caps unknown
key switches clicky = buckling spring (assumption from the part number)
I'm sure after another few years, someone will find this thread and add to the information here. It might take another decade or so, but I'm pretty confident we'll get to know the history behind this variant someday.