I have a 1984 300d td. upon further research it shows that it has a w123 chassis, produced from 82-85. my real question (that i seemed to have some difficulty in getting answered in regular interweb searches) is what does the "w" and the "123" mean in terms of the chassis? wheelbase? length? wagon?

 

Wow, nobody here has taken a stab at answering this question ?
I guess in the big scheme of things it is not really a relevant or important thing to know, but I will give it a try.
Origin of the w in front of chassis number originated before World War 2, maybe even WW1.
Every model or different chassis design / series received a 3 digit factory designation (originally maybe even 2).
Off that chassis you would have different engine choices.
The cars had a W (example 180)
and the engines got an M plus 3 digit 'code.
W standing most likely for 'Wagen' (german word for Car/vehicle and the M standing for 'Motor').
With the start of the diesel engine they added an 'OM' standing for Oel-motor.
These were factory internal designations just for ease of parts number cataloging and reference.
A W180 chassis by example (a 1955-1959 220S) could have a M180 motor (2.2liter gas) or an 'OM 636 motor ( 1.7 liter diesel motor) or even other motor .
The numbers could occasionally coincide and create confusion (as in this case), or even worse, they get mixed with a Model designation as in this example (180, or 180 Diesel...)
A 180D (Example: 1953-1961) model however had a W120 chassis with either an OM636 or an M121 engine.
I am fairly sure about most of this.
The W could also stand for Werks-intern (German for Factory internal).

The car you have is a (W)123 193 etc. (my guess) or maybe a 300 diesel sedan (123.133) ?
If an '84 your VIN would start WDBAB93... or WDBAB33....)
To avoid people giving the wrong model number/designation as you may have hereL
What you have is a 300TD, 1984 or a 300D.
When you add letters or change them around you are changing and confusing chassis and motors.
A 300TD is a station wagon (T for transit, D for diesel NOT Turbo Diesel).
A 300TD, turbodiesel is a Turbo diesel station wagon
A sedan is a 300D (TurboDiesel=(TD in brackets) or non-turbo),
A Coupé would be a 300CD (maybe Turbo Diesel, maybe reg Diesel)
If it was a turbodiesel, that would be the second prt of the chassis designaton W123 (body) 133 (3 liter turbodiesel) or 193(3 liter turbodiesel wagon).
To confuse matters even more: in the early eighties (I think first year 1981) Mercedes replaced numbers with letters, where the chassis (VIN) would now be a
WDBAB33... for the same car, but the US market only .

In recent history (Nineties) some people, maybe even Mercedes started using the letter S as in S123.
But I believe only for the newer (90ies and up) chassis/cars....

 

Touring is BMW
Transit for Mercedes