The Westerly Collection guitars are made in China and I bet your F-150 was made at GREE (Grand Reward Education & Entertainment, the GREE factory is located in Guang Dong province, in southern China.)
They were intruduced in 2015:
http://guildguitars.com/introducing-the-westerly-collection/
http://guildguitars.com/g/westerly-f-150/
Regarding the Serial Number and year of manufacture and Country of origin: You can find it on a black label on the neck heel inside!
Here is an example of a recent 2017 model, your F-150 will use a different (older) serial number system as explained below.
The neck block label numbering is not easy however...
For the China made models it starts with "G". But the system was changed already since 2015.
Originally in 2015 they used a 8 letter/digit serial number and it always started with G1 = Guild China, most probably GREE factory.
A D-120CE for instance has G1
157208 as serial number which is year 2015.
Now the Arched back models use "G2" but they are still Made in China. For instance G2172173.
So the number behind "G" seems to means something else, it could be the specific factory used or simply 100 series vs. 200 series.
But there might be a possibility that the arched back models are not made at GREE but a different Chinese factory, hence the G2.
So G1 might mean made by GREE and G2 another factor in China. Maybe. Maybe not.
Anyway, the next two numbers after G1 or G2 were the manufacturing year (like 15 stands for 2015) and the last 4 digits are the running numbers for a max of 9,999 Guild Westerly Collection guitars per year from China (at that time)
At least that was my understanding so far.
Now it starts to get really confusing as a D-120 and a F-1512E I recently found have no longer a 1 or 2 after the G ! They only have G and 6 to 8 numbers afterwards!
The serial is simply G170693 as example, as shown in the picture above. Anyway, the 17 is again the year 2017.
So my new theory is:
As the new California produced 2017 guitars have serial numbers like C170815 (a D-20 as example where C stands for California) maybe CMG changed the system for GREE as well and GREE made Guild Acoustics from some point in 2017 onwards simply use G with 6 to 8 numbers behind.
The latest arched back Westerly Collection guitars also use a new style label with "Designed in California" and a different Guild logo, compared to the 2015 style label:
Hope it all clarifies your questions.
Ralf