There are examples of where on a Montesa to find the ID at the bottom of the page. Not all VIN's are where they are in the first two pictures, but on the steering head like in the last picture.

Type:
02=Impala 175cc
03=Impala 175cc Sport
10-Cota 25 Trials
11=Cota Trials 4-speed 250
12-175 Texas
13=Diablo 250cc
14=Enduro 175cc
18=Cappra MX 125cc
19=Cota 172cc
20=Cota 49
21=Cota Trials 5spd 250cc
23=LaCross 250cc
24=Scorpion 250cc
25=Impala Sport 250cc
27=Mini Moped
28=Cota Trials 6-spd 125cc
30=Scorpion 50
33=Cappra 250cc
34=King Scorpion 250cc
36=Cappra GP MX 360cc(early)
38=125 VA
43=Cappra GP 5-spd 250cc
44=King Scorpion "Automix"
45=Rapita 250
46=Cappra GP 360cc
50=Cota 25C
51=Cota 348-349
53=Cappra GP 4-spd 250cc
54=Enduro 250
63=Cappra MX 250cc
66=Cappra 360 (1976 up)
73=Cappra 250 (1974 up)

Here is an example of the parts numbering system: 21.60.03801,
21-Cota 5-spd, 60-engine group, 03801-head pipe
Here is another, 02.30.010= 02=Impala, 30=front fork, 010=crown

Here are the Group numbers:
20=Frame
30=Front fork
35=Lower fork
40=Rear suspension
50=Wheel & Hubs
55=Brake
60=Engine
61=Ignition
62=Carburetor
63=Clutch
64=Transmission
65=Kick starter
66=Gear change
70=Lighting
80=Speedo & Horn
87=Tools
90-99=Hardware
Prefixes 5,6,7,12,15, D, H, & U are miscellaneous components.
0/000 thru 000/000 are AMAL carb. components.

53m Montesa