As an engineer, I realize the reasoning for frowning upon expressions where an "s" is added to the unit, to make it plural.

"120 volts" shouls be abbreviated "120 v." because the "s" would seem like we are multiplying volts by seconds.
My question, however, pertains not to the world of science, but to daily usage. Suppose we are talking about the "pound" as a monetary unit. Is it correct to write: "150 lbs."?
Can someone please provide a reference in which the "lbs." is used?

TIA,
-Ramon
As an engineer, I realize the reasoning for frowning upon expressions where an "s" is added to the unit, to ... it correct to write: "150 lbs."? Can someone please provide a reference in which the "lbs." is used? TIA, -Ramon

It is NOT correct to use either lb or lbs when writing about the pound as a monetary unit - lb and lbs are only used when describing pounds as units of weight.
If you want to write about currency rather than weight, either use the £ symbol or the 3-letter ISO currency code (e.g. GBP for the monetary units used in the UK).
Okay, point taken.
In that case, I would like to modify my question:
Can someone please point out to an instance of a respected source using "lbs"? I have a bet with a colleague engineer who insists that the engineering (physics, math, etc.) is the one and only way.

I claim that in layman day-to-day, or even New York Times type of English, it is permissible in fact, recommended to add the "s" at the end when writing about plural units.
Thanks,
-Ramon
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Okay, point taken. In that case, I would like to modify my question: Can someone please point out to an ... a bet with a colleague engineer who insists that the engineering (physics, math, etc.) is the one and only way.

So what's in it for us? You have the bet, but you want us to do the proving for you.
Try putting something like lbs .

TSH
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So what's in it for us? You have the bet, but you want us to do the proving for you.

Worldwide acclaim? Thunderous applause? The reverence of your peers? Ain't that enough?
-Ramon
Suppose we are talking about the "pound" as a monetary
unit. Is it correct to write: "150 lbs."?

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Students: We have free audio pronunciation exercises.
So what's in it for us? You have the bet, but you want us to do the proving for you.

Worldwide acclaim? Thunderous applause? The reverence of your peers? Ain't that enough? -Ramon

I'm not after worldwide acclaim, and I doubt that 'Lyndon says so' would be a good enough reference to win a bet, but the question intrigues me. I suspect that guides to technical writing would recommend using the singular form. As an engineer I am aware that I should use 'lb' and not 'lbs' for the reason that you gave. However I frequently use 'lbs' and similar plural forms, and I believe it to be common practice. If I wanted to abbreviate 'pound seconds' I would probably write 'lb secs'. I would never interpret 'lbs' as 'pound seconds'.
I am much less likely to use a plural form when working in SI units than when working in Imperial. The SI system imposes a discipline that is not present in Imperial measurements. There is no doubt that in 'layman day-to-day' English it is permissible add the 's' to 'lb'. The proof is that it is very common useage (google lbs + weight as suggested elsewhere). So you win the bet - and you can tell the other guy 'Lyndon says so' if you like.
Lyndon
Absolutely. In fact it is less likely to be misenterpreted than "pounds" which could be enterpreted as the currency unit.

JK