Seller: thekeyboutique (3,087) 97.8%, Location: Pittsburgh, Pennsylvania, Ships to: Worldwide, Item: 263574516443 Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Thank you for stopping by The Key Boutique! This listing for for a vintage all brass Popular Progress clock key number 1 (metric) which will fit a square post that is 2.5mm. The squares on the graph board are each a half inch and that should help in gauging the size of each different key. Please see below for a detailed explanation of clock key sizing (Standard Vs. Metric). We have several other kinds of keys listed, both new and old, so be sure to check out our items for sale page! We are happy to offer combined shipping which should be done automatically upon checkout, but if for some reason it is not, please let me know and I will get a corrected invoice right over to you! Shipping: Items will be shipped out as soon as payment is received. Sales Tax: Members from Pa will have to pay 7% sales tax. Thank you for stopping by and be sure to check back as more keys will always be being added. Have a great day! Reference No. KB2320 Explanation of Clock Key Numbers and Sizes. Just as there are 2 different numbering systems throughout the world (standard and metric) there are also 2 different clock key size systems, the English (Standard) and metric (Swiss). They are very close in sizes but moves in different increments. The standard sizes differ by .2mm per size, and the metric sizes differ by .25 increments. The Metric scale is as follows: Metric Key No. Size in mm 000 = 1.75 00 = 2 0 = 2.25 1 = 2.5 2 = 2.75 3 = 3 4 = 3.25 5 = 3.5 6 = 3.75 7 = 4 8 = 4.25 9 = 4.5 10 = 4.75 11 = 5 12 = 5.25 13 = 5.5 14 = 5.75 15 = 6 And the Standard scale is as follows: Standard (Sometimes referred to as ‘English’) Key No. Size in mm 000 = 2 00 = 2.2 0 = 2.4 1 = 2.6 2 = 2.8 3 = 3 4 = 3.2 5 = 3.4 6 = 3.6 7 = 3.8 8 = 4 9 = 4.2 10 = 4.4 11 = 4.6 12 = 4.8 13 = 5 14 = 5.2 15 = 5.4 As you can see by the size scales, the sizes are close, and they intersect at size 3 so a size 3 clock key will fit both a standard and metric clock just as it should. The clock key should fit perfectly over the post with no ‘play’, or wiggle room. It should be very snug if a proper fit, but as you can see in the charts, key No. 2 between the 2 sizes is a difference of .05 which is hardly even noticeable, but you will see some play. This also means you would need to be careful when purchasing a clock key because if your clocks winding post is a standard system 2 (2.8mm), then a metric system no. 2 key will not work because it would be too small to fit over the post being .05mm smaller than the post itself. The best thing to do if you are unsure of the size you need is to measure the clock’s winding post that you need a key for, and use these guides to help with your purchase. If you purchase the correct number, like I said above, it will be a perfect fit with no movement on the post at all, but both systems move up in such small increments that the next 2 sizes will also work, so if you need a standard No. 5 key, a standard No. 6 and 7 key would work as well, though there would be some movement between the post and the key if not the exact number. You will also notice that in some auctions a key will be numbered on the body of the key itself, but does not actually fit the dimensions of that number on either size scale, so you may see a key that is numbered with a 9, though it is actually a metric 7 and standard 8. I do not know why this is though I am looking into it, but please note that whatever size any key is listed as, that number is based on the true size of that keys square hole. If you have any other questions or need any additional clarification, please do not hesitate to contact me as I am always more than happy to help as best I can. Thank you again for checking out my items, and have a great day! Condition: Used, Condition: Great condition for age!