[Vintage-Audio] Re Audio Tape Differences

[Duane Fischer, W8DBF]

Greetings All,	
	
Do any of you know why Scotch (3M) seven inch reel audio tape number 227 is far
heavier in weight than number 150? Both are 1800 feet. The number 150 says 1
mil, the number 227 does not state the mil at all. 	
	
I recently purchased some of the Scotch number 150, still wrapped. However, the
tape is brittle from improper storage and not useable. No protective wrapper on
the tape inside the cardboard box either. The ones I used to buy in the sixties
and seventies were wrapped.      	
	
Now the Scotch number 227 is another story. I think it may be mil spec surplus,
still sealed too. The tape inside each box is also inside a plastic protective
wrapper. This tape still has a 'fresh' scent to it! This tape is in excellent
condition. 	
	
When one picks up the two tapes, the weight difference is immediately obvious.
No, it is not from the plastic reel, they are quite similar in appearance. Was
there a difference in the military tapes? If so, what were they?  	
	
Thanks to whomever can help.        	
	
Duane W8DBF