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His frock hung loosely, exposing his round throat, mossy chest, and short and nervous arm embossed with pugilistic bruises, and quaint with many a device in India ink. - Herman Melville

quaint
a : marked by skillful design <quaint with many a device in India ink — Herman Melville>
[M-W's Col. Dic.]

Question 1:
Had his arm been tattooed using Indian ink?

I believe "device" is used in one of the following senses.

device

1 b : something fanciful, elaborate, or intricate in design
3 : an emblematic design used especially as a heraldic bearing
[M-W's Col. Dic.]

Question 2:
Even when a frock is not hung loosly, a throat would be clearly visible because a frock covers body area below the neck. Is he referring to some particular frock?

Question 3:
"many a device" - I would have written 'many devices' instead. What's the difference between the two?

Please help me with the above questions. It would be kind of you. Thanks.
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Question 1:
Had his arm been tattooed using Indian ink?-- Yes

Question 2:
Even when a frock is not hung loosly, a throat would be clearly visible because a frock covers body area below the neck. Is he referring to some particular frock?-- Round hroat and hairy chest: this is the view Melville wishes the reader to conjure up. He is not concerned with the detail of 18th century shirts.

Question 3:
"many a device" - I would have written 'many devices' instead. What's the difference between the two?-- None except that nowadays 'many a' is distinctly literary. It may or may not have been so in Melville's time.
Comments  
Students: Are you brave enough to let our tutors analyse your pronunciation?
Thanks a lot, Mr Micawber.

If "many a" is higher register, then what would substitute it in informal or modern form as you have already turned down "many devices"?
Where did I do so?
Sorry. I misread you.
Students: We have free audio pronunciation exercises.