ID lionel part 611? engine or e-unit

That is a clip to join the center "rail" of super "O" track. It is not a part of your engine.

C.W,

Thanks! I don't have any super O track, well that wouldn't surprise you. I'm a Lionel novice, and this 611 is my first postwar Diesel. Finally my boxcars have a proper motorised friend now. The 611 came in two different loads as I was lucky this time on the net, scoring a separate pick up truck and the remaining parts from two different sellers. The only missing part was a horse shoe clip, I'll find one in my scrap box.

Risky evening that was, the truck was easy but the other part some eager guy didn't give up that easy.

I'm impressed by the quality, that body moulding being some 50 years old now. Plastic kits from my childhood were far less crisp. And it's some thrill, having such an engine in hands, after craving and longing and only seeing them on pictures.

Have a nice day,

Kieffer

This could also be the part that is inserted into several accessories.  It was designed for accessories like the cattle car, milk car and log loader.  If you had O27 track you used the lower profile clip 3656-67, if you had O track you used the larger 3656-66 clip.  The clip provided the appropriate height for power to reach the collector shoe tt-208.

A little hard to tell from the small picture, however enjoy you new/old post war engine.  They are durable and easily repairable.  Have fun.....

The part is a super O joiner, as I wrote.

Here are pictures of the parts for the Cattle car and such (lifted from the web):

It is a Super 'O' center rail clip as CW identified, not a operating car clip.