I'm thinking of a train class..

[sprite]

class 73
-Doon Sooth
- flip 73 -> 37, a moderately well known class.

 

[Schnellzug]

Clever, but it's, once again, not the wright answer I'm afraid.
The area in which they operate is a very limited area, a very very limited area, in fact.

 

[Class172]

Class 139?

 

[Schnellzug]

Class 139?

You'll laugh when you see what it is.
No, but the area of operation is not dissimilar in terms of distance. :-/
Another clue, before I have to go on & leave it again for now; this is a type that is in service today on UK standard gauge rails , not a heritage line, but has never had a TOPS number.

 

[Temple Meads]

The locos used on the EuroTunnel motorail services?

 

[Schnellzug]

The locos used on the EuroTunnel motorail services?

Is the winner!!
Noteworthy features: Last locos built by Brush; first & so far only triple-bogie locos used in the UK (if only just); most powerful locos in the UK (I think); limited area of operation: Channel Tunnel to Dollands Moor; numerical similarity with another type: they were (originally, at any rate) numbered 9000 etc, like the Deltics.

 

[Temple Meads]

Ah nice, an unexpected surprise

1) We were/are important but no one seems to remember us.
2) We have/had at least 2 major flaws.

 

[Class172]

Class 24?

 

[gg1]

The prototype PEP units?

 

[Schnellzug]

Continuing the widely disparate suggestions, the APT (class 370 version)?

 

[Temple Meads]

The prototype PEP units?

Excellent, and correct, the 2 flaws are the lack of a lavatory, and the fact they couldn't couple to more conventional units, and they're important as the forerunners of more modern EMU's.

 

[gg1]

This one shouldn't be too hard.

This small class is currently in operation on the national network, it differs from another numerically much larger class in one small but very significant way.

 

[Ivo]

Class 159?

 

[150222]

Class 171?

 

[gg1]

Class 171?

Correct, differs from the 170 in the type of coupling used.

 

[150222]

*We are related to a non-standard class.
*We have an unusual featre for a train of this type.

 

[Class172]

Class 180?

Open floor if correct.

 

[150222]

Nope.

 

[gg1]

Class 91?

(related to the APT and having different shaped cabs)

 

[150222]

No not a 91.

 

[hmp455]

Class 319?

 

[150222]

Nope but your closest so far.
*We often operate in multiple with a similar class.

 

[Peter Mugridge]

Class 456???

 

[Temple Meads]

Class 465?

 

[150222]

Nope but both closer still.

 

[Schnellzug]

466 often work in multiple with a similar class (465), but I'm not sure what the unusual feature mgiht be.

 

[150222]

Correct at last!
The class they often work with are 465's.
The unusual feature is that they are a 2 car EMU.
The non standard class they are related to are 165/166 (gauge).

 

[Schnellzug]

Ah, thank you.

Well, let's see if I'v got another one.

Ah,
* this class or type is or was notable for a number of reasons;
* this class or type operates or operated in a specific corner of the Land;
* and this class or type is related numerically to another well known class.

 

[sprite]

Class 43 (the NB built locos NOT the hst power csrs)

 

[Schnellzug]

Class 43 (the NB built locos NOT the hst power csrs)

You are too clever. For that, you get a Cake.