DA-Q marked slides were made for QHMC by A. Dalkin and Co. of Chicago.
The type A variation 3 slides with the rear flat cut and narrow Arm Joint were often found with the letter U on the outside bottom.
Don't confuse a UN-Q for a Un-Quality slide either. These were made for QHMC by Union Switch and Signal Corp. The same maker who produced the receivers for QHMC called Un-Quality.
I compare that Larson book to the Friday night Hooker who will tell me I'm the best and that she's still a VIRGIN !!
HTH,
Charlie-painter777