According to the applicant, this transaction was effected on 22 April 1977, as is proved by the copy of the order sent by Jouret to Socothy, the marketing company of Thy-Marcinelle et Monceau.

The defendant points out that the agreed price was that of the Soco pricelist in force at the time of despatch, in accordance with the applicant's practice. Since the invoices were drawn up and delivery took place after the entry into force of the minimum prices the latter should therefore have been observed; in fact they were not, as they were undercut by the use of market discounts given by means of credit notes.

The applicant replies that a transaction may be effected before delivery and the issue of an invoice, which are distinct from the transaction itself, the latter being an agreement by which the parties decide on the subject-matter of the sale and on the price, even if the latter is only ascertainable subsequently. In fact the price was determined at the time of the conclusion of the contract and this is evidenced by the fact that it is quite clear that if, when issuing invoices, Thy-Marcinelle et Monceau gave discounts by means of credit notes it was not because it felt a sudden wave of generosity, towards the buyer but solely because it was acting upon a firm agreement to which it had given its word.

Even if certain conditions to be applied are those of the pricelist in force at the time of despatch, the fact remains that the final prices, that is to say the prices and any discounts, are thus fixed at the time when the contracts are concluded despite the impression given by the documents which contemplate application of the price on the day of despatch. That contradictory situation is explained by the special circumstances prevailing on the steel market and by the obligation to publish and apply pricelists. It was in fact the alignment of prices on those of competitors which led to the general undercutting of prices and the practice of using credit notes to bridge the difference between list prices and the prices agreed at the time when contracts were concluded.

Moreover, it is difficult to see why the applicant should have observed the minimum prices for transactions subsequent to 9 May 1977, when it had given discounts during the same delivery period on earlier transactions, if it was not to honour its word. The applicant could produce evidence to prove the propriety of its conduct.

Finally, the application of the disputed general decision to earlier contracts means giving it retroactive effect.

The defendant replies, first, that witness evidence cannot be adduced against a written document whose text is clear and unequivocal and, secondly, that it is legitimate to apply a general decision to an element of the contract (the prices to be charged) which was to be fixed on the day of despatch, that is to say subsequent to the entry into force of the decision. In effect, the minimum prices replace the company's own list prices.

The defendant points out in passing that the applicant admits to having undercut the prices on its own pricelist but that it deliberately decided not to take action against it for that offence — although not admitting as much — and that it chose to impose fines only in regard to conduct constituting a breach of Article 61 of the ECSC Treaty.

The applicant states that this transaction was effected on 21 April and it produces confirmation from Dema which on 22 April 1977 spoke of the price agreed between us.

The defendant, with an argument parallel to that relating to the previous transaction, replies that the invoice was issued and the goods delivered after the entry into force of the minimum prices system, and at prices lower than those prices due to the discounts accorded in the credit notes.

The applicant stated in Case 26/79 that the transactions with Etablissements J. Champion were effected under a consignment contract. In such a case, on the last day of each month a provisional invoice based on a theoretical estimate of deliveries is drawn up. Of course, such invoices cover earlier withdrawals from the stock maintained at the customer's premises. The customer then sends off as soon as possible a statement summarizing the actual withdrawals shown in its inventory on the last day of the month and a corrective invoice or a credit note for the difference is issued.

The parties put forward arguments on this subject which do not now need to be stated since the amending decision of 2 May 1979 impugned by Application No 86/79 no longer takes into account the transactions with Etablissements Champion.

The applicant states that the Commission focused on three transactions with Etablissements Davum in its first decision.

The first two — which are still in suit after the second decision — are alleged to have been effected on 5 and 6 May 1977 respectively, that is to say when the application of the minimum price system was not yet compulsory. This is evidenced by two telex messages sent by Davum to the Paris office of the applicant.

The defendant points to invoices and despatch dates and replies that the invoiced prices are in accordance with the pricelists in force at the time of delivery but that they have been discounted by credit notes, which amounts to an undercutting of the minimum prices in force at the time of the performance of the transactions.

The parties then refer to the general arguments set out above regarding the sales to Jouret.

The parties also dealt with the third transaction with Davum but, since the amending decision of 2 May no longer takes it into account, there is no need to summarize their arguments on this subject.