As has already been mentioned, but is worth repeating, income from any source is taxable, regardless of whether anyone sends the IRS a 1099 reporting that income. And since people can make mistakes, receiving a 1099 that indicates income was reported to the IRS does not necessarily mean that you have taxable income.* You are required to calculate your income yourself. The 1099 reporting rules are there for the IRS to know about payments made by businesses that want to deduct those expenses, and thus need to be reported as income by someone (if subject to US tax). You receive a copy of the 1099 as a courtesy; whether you receive it yourself has no bearing on whether the IRS receives it. If the latter happens and not the former the payer might be in hot water, but whether you receive it or not has no bearing on whether it’s income.
*I had a client receive dozens of 1099-NECs for no good reason due to a computer glitch. The payer corrected all of them with the IRS, but didn’t bother to send the client the corrections. The client was freaked out, but since they were all mistakes, he didn’t have to report them, even if they hadn’t been corrected by the payer. I found out they were corrected by the payer by getting him to get a Wage and Income Transcript, which showed the corrections that were filed.
Now when you’re selling stuff, rather than services, you generally have some cost to acquire the stuff, known in accounting as Cost of Goods Sold. If the stuff you’re selling you acquired for reasons other than to resell it, then you actually have a capital gain, not ordinary income. It’s unclear from the OP what’s the case here. You restored the items and are selling them, so I guess you bought them and restored them in order to sell them, but that’s not necessarily the case. You could have had them on display for awhile and then decided to get rid of them. In that case, things work a little differently, and I’ll go through each separately.
If this activity of restoring and selling machines was undertaken over a period of time with the intention to make a profit, then you have a trade or business, and report all the activity involved with the business on Schedule C by default. You first list your gross receipts, then subtract the Cost of Goods Sold to arrive at gross income, then subtract all the other expenses you incurred in the business for the purpose of restoring and selling them that are not Cost of Goods Sold to arrive at net income. There’s really no difference between Cost of Goods Sold and other expenses except for a few niche situations where it matters that Cost of Goods Sold is subtracted before arriving at gross income. If net income is at least $400 or so, you’ll pay self-employment tax on the income as well as income tax, which is 15.3% of “earnings from self employment”, the latter of which is defined as 92.35% of your net income from self-employment. This is because you get to deduct half of the self-employment tax for income tax purposes, as it’s basically the employer half of FICA.
All the activity on Schedule C is completely unrelated to the deductions that you take on Schedule A, known as itemized deductions. In reality, Schedule A deductions in general are kinda fake. They by and large don’t represent any actual reductions in your income, but are certain deductions allowed by Congress for whatever policy reason they devise. Some of them make sense (Medical), some of them really don’t (mortgage interest). There aren’t very many types of such deductions, and because practically all miscellaneous deductions are currently not allowed, they are simple to list: Medical (in excess of 7.5% of your income), Taxes (limited to $10,000), Interest (but only mortgage interest and investment interest), Charity (with various limitations depending on what and to whom you give), and Gambling Losses (to the extent of Gambling Winnings, but if you gamble as a living, that goes on Schedule C).
Now if you didn’t intend to do this for profit, that makes things much worse for you under current law, which does not allow any deductions for the production of income for activities not for profit. If you ask me, that’s unconstitutional, but the lobbying and legal power of hobbyists is minimal, and most of them are going to simply ignore the law anyway and claim they were trying to make a profit. Note this is one case where it matters what’s Cost of Goods Sold, because you can always subtract COGS to arrive at gross income, even if the rest of the deductions are not allowed. You would have to report all the income as “Other income” at the bottom of Page 1 of Schedule 1, the Cost of Good Sold on a specific line on Page 2 of Schedule 1 that I’m not going to look up now. At least in this case you avoid self-employment tax, because that only applies when attempting to make a profit.
If you didn’t intend to profit though, it’s more likely that you didn’t buy and restore them intending to sell them. In that case, as mentioned above, you might have a capital gain. If that’s the case, you need to add up all the expenses you incurred in buying and restoring the machines, and that’s what’s known as your basis in the machines. You report the sales on Schedule D and Form 8949, checking either Box C or F depending on if it was held long-term or not. You take the gross proceeds and subtract the basis to get the net capital gain. If you had a capital loss, you’d have to adjust the loss to zero because you can’t take losses on activities not for profit. Or you could simply not report the sale if the IRS wasn’t told about it - there’s no point in including it if there’s a zero bottom line and the IRS isn’t expecting to see it reported. In this case it’s hard to say that you were trying to make a profit in restoring these machines but didn’t initially intend to sell them. That would only be the case if you at least at some point planned to use them in a business some way other than selling them, and the IRS would want proof you were considering that if you claimed a capital loss on these items.