I have checked all old coupons and price is $7.99 for Dovetail Marker Guide Dovetail Making Jig (in Banggood). Price history, coupons and price alert are available on this page. Let’s see what best price is ATM.
Dovetail Marker Guide Dovetail Making Jig Aluminum Alloy Featuring 1: 5 1: 6 1: 7 1: 8 Slopes for Woodworking DIY Wooden Joints – Black
Latest price update (UTC time):
Banggood ($7.99)
Banggood warehouse is located in China. There are no active coupons for this product, but the price is pretty low isn’t it? Is it good price? From what I can see this price is higher than average price ($5.95).
Link: Banggood product page
Price: $7.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGWDT15, BGa1359e
(I don’t think these’re gonna work, but you can try ’em out anyway)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for Dovetail Marker Guide Dovetail Making Jig.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).