There is not much to go on with this L-Arm without the top section.  It is for sure not a standard L-Arm with the one end being the way it is.  I can't pinpoint exactly, but the way it is made the bottom of the L-arm looks like it would bolt down to another stand.  Possibly an accessory stand.  This will take some pondering.  Their is one guy out there that knows exactly what you have, but it will take time for them to respond or see this post.

If I had to guess, I would say this looks like a piece from an old-time Trap table that was mounted over a Bass Drum.

Thanks for the input . . .  

If anyone recognized it, let me know!

Member kdg is correct.

Old Leedy and perhaps other brands' catalogs often showed trap assemblies with arms that attached like these.