Having grown up in the tail end of the steam era, I always thought the NKP Berkshires looked "all businesss" with the additional Mars Light. Same for Chcago, Burlington & Quincy 4-6-4's, 4-8-4's and 2-10-4's. I liked 'em!

On the Berks they look naked to me w/o them, overall on the roads that installed them I personally liked them.

Rusty

I felt safer working on locomotives with gyralites (Frisco) because they draw extra attention at grade crossings. 

From a fan aspect, my favorite railroads had them on both passenger and many freight locomotives (SLSF and FW&D).

The Mars lights on the above Northwestern Steel & Wire ex-GTW 0-8-0's came from Burlington locomotives awaiting scrap at the plant. 

It depends on the locomotive for me. I personally prefer the way 765 looks without a Mars, but I think an EMD early cowl unit (like an E) looks better with both Mars and regular headlights. A GS4 with a Mars also looks better, IMHO, than a GS2 without a Mars.

I can remember back in the '80's when the Mars light on 765 was on and working...

 I like them.

Long before 4449 became functional again. The Espee installed Mars lights on what seemed like every engine on their roster. I grew up with our house shaking and the long shadows cast through our windows by the Mars lights.                                 

To be clear, the SP GS-4 class northerns were delivered from Lima Locomotive works with Mars Lights (no red feature). No other steam locomotives on SP had Mars lights except those GS-4/GS-5 steam locomotives, until diesels were delivered. The diesels all pretty much came from the factory with Mars or Pyle National Gyra-Lights. 

I used to think that Mars lights looked great on Baldwin sharks.  They used to come snarling through my home town on the PRR main line, hauling enormous coal drags, Mars lights gyrating and horns blaring as they approached the crossing.

I sure like them on fire trucks and other emergency vehicles...

A great looking fire truck - a bank of Mars lights, a nice bell, and a Federal Q - all out front to be seen and heard!

In the 1960s while traveling at night on US31 north of Bowling Green Ky and roughly parallel to the L&N, the Mars lights could be seen in the sky for miles before encountering the trains. Weird 'till you figured out what was going on!

I thought only the first two Pennsy BP-20's had mars lights.

I'm not aware any RF-16's, Pennsy or otherwise, that had Mars lights installed.

Rusty

To answer the question posed by this thread:  I personally like the appearance of NKP steam with the Mars light, because they all had them when I was growing up, and I seldom saw a photo of one without a Mars light.  It looks normal to me.  However, they are also good looking without.

Now, here's a question of my own:  Since Pennsy only had a couple of Sharks and a couple of E8's equipped with Mars lights, does anyone remember ever having seen one of those engines with the Mars light in use?

Here is my prized collection: Working Mars light model, 250R, saved it from scrapper's torch at Alter's at Council Bluffs, Iowa. C&NW sold old wrecking crane to Alter's. That 250R once used on C&NW steam locomotives and early Geep before put it on wrecking crane. My friend was able to build special transformer that work from 120V AC to 64V DC and it worked!

C&NW wrecking crane #6353 before heading to Alter's for scrap. 250R light can be seen at left top of crane.

After cutting up at Alter's. 250R light can be seen at lower left by the ground just below of C&NW gondola car.

Now I am going to make an assumption here: the red oscillating warning lights employed on Union Pacific and Milwaukee Road 4-8-4's and Milw 4-6-4's were Mars Lights. On the Milwaukee, they counter-balanced the somewhat jarring appearance of the Milwaukee's off-set bells - and were esthetically succesful. All of these applications enhanced the appearance of the locomotives - adding some additional color and an air seriousness. Of course, just opinion!! One man, one vote!

From Wikipedia:

Mars Light

Design variations

There were many models of Mars Lights, which used several methods to oscillate the beam. Sometimes the bulb and assembly were moved, other times a reflector behind the light was rotated. The beam was usually rotated in a triple eight pattern, providing a source for the company slogan, "The Light from Mars". The beams came in a variety of shapes and colors, some locomotives having red and white lights.

Railroad use

 

Many railroads used Mars lights on a variety of locomotives, both steam and diesel. Mars lights are no longer used by railways, having been replaced by ditch lights, with the exception of some passenger carriers, such as Chicago's Metra. They are still used on fire fighting apparatus, and are available from Tri Lite / Mars, located in Chicago, Illinois.

LAFD requirement

The Los Angeles Fire Department required Mars lights as a standard LACoFD warning device until the Federal BeaconRay was adopted as a replacement.^[1]

Gyralite

Gyralite is a similar type of gyrating warning light formerly made by The Pyle-National Company and now by Trans-Lite, Inc.^[2]

See also

• Grade crossing signals

References

After so many years, I can't answer your questions.  I just know that they had the distinctive Baldwin sharknose styling, they were hauling coal and they had Mars lights.  I confess, I don't know what models they were.  At age eleven, I thought I was pretty hot stuff just knowing they were Baldwins.